Optical module, optical module mounting method, optical module-mounted circuit substrate, optical module evaluation kit system, circuit substrate, and communication system

ABSTRACT

An optical module includes a housing including an internal space that has an opening in a substrate mounting surface, an element mounting surface that forms a portion of an inner surface of the internal space, and a waveguide introduction opening that is formed in a side surface intersecting the substrate mounting surface and is opened to the opening of the substrate mounting surface and communicated with the internal space, an optical element that is mounted on the element mounting surface, and an electronic element that is mounted on the element mounting surface and is connected to the optical element. When the substrate mounting surface is mounted on a circuit substrate, an optical waveguide that protrudes from a surface of the circuit substrate is introduced into the internal space through the waveguide introduction opening.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.14/987,016 filed Jan. 4, 2016, which is a continuation of PCTInternational Application No. PCT/JP2013/068563 filed on Jul. 5, 2013,the entire contents of both of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an optical module, an optical modulemounting method, an optical module-mounted circuit substrate, an opticalmodule evaluation kit system, a circuit substrate, and a communicationsystem.

2. Description of the Related Art

Optical interconnection between boards has been studied in order toachieve exascale computing. In the optical interconnection, an opticalmodule which is an optical transmitter or an optical receiver transmitsor receives optical signals through an optical transmission line.Japanese Laid-open Patent Publication No. 2004-29621, Japanese Laid-openPatent Publication No. 2000-98153, Japanese Laid-open Patent PublicationNo. 2002-189137. Japanese Laid-open Patent Publication No. 2003-139979,and Japanese Patent No. 5117640 disclose a structure in which an opticalmodule and an optical transmission line are formed on a circuitsubstrate.

SUMMARY OF THE INVENTION

It is an object of the present invention to at least partially solve theproblems in the conventional technology.

In accordance with one aspect of the present invention, an opticalmodule includes: a housing including an internal space that has anopening in a substrate mounting surface, an element mounting surfacethat forms a portion of an inner surface of the internal space, and awaveguide introduction opening that is formed in a side surfaceintersecting the substrate mounting surface and is connected to theopening and the internal space; an optical element that is mounted onthe element mounting surface; and an electronic element that is mountedon the element mounting surface and is connected to the optical element.When the substrate mounting surface is mounted on a circuit substrate,an optical waveguide that protrudes from a surface of the circuitsubstrate is introduced into the internal space through the waveguideintroduction opening.

In accordance with another aspect of the present invention, a circuitsubstrate includes: an optical waveguide that protrudes from a surfaceof the circuit substrate; and the optical module according to an aspectof the present invention that has the substrate mounting surface mountedon the circuit substrate such that the optical waveguide is introducedinto the internal space through the waveguide introduction opening.

In accordance with still another aspect of the present invention, anoptical module-mounted circuit substrate includes: the optical moduleaccording to an aspect of the present invention; an optical couplingmember that is optically coupled with the optical module; and a circuitsubstrate on which the optical module and the optical coupling memberare mounted and which has a main surface having an opening formedtherein and is electrically connected to the optical module. Thepositioning of the optical module and the optical coupling member in atleast a horizontal direction of the main surface of the circuitsubstrate is performed through the opening.

In accordance with still another aspect of the present invention, anoptical module evaluation kit system for evaluating an optical module,includes the optical module-mounted circuit substrate according to anaspect of the present invention.

In accordance with still another aspect of the present invention, acommunication system includes: the optical module, the circuitsubstrate, or the optical module-mounted circuit substrate according toan aspect of the present invention.

In accordance with still another aspect of the present invention, anoptical module mounting method includes: placing the optical module anaspect of the present invention such that the substrate mounting surfacefaces a circuit substrate; aligning three alignment guide holes whichare formed in the housing so as to extend from a surface opposite to thesubstrate mounting surface to the substrate mounting surface with threemarkers which are provided on the circuit substrate so as to correspondto the arrangement of the three alignment guide holes, while observingthe three markers through the three alignment guide holes, therebyaligning the optical module with the circuit substrate; and mounting thealigned optical module on the circuit substrate.

In accordance with still another aspect of the present invention, anoptical module mounting method includes: attaching, to the opticalmodule according to an aspect of the present invention, a protector thatcovers and protects a surface from which the optical element is exposed;and mounting the optical module on the circuit substrate, with thesubstrate mounting surface facing the circuit substrate.

In accordance with still another aspect of the present invention, anoptical module mounting method includes: mounting the optical moduleaccording to an aspect of the present invention on the circuitsubstrate, with the substrate mounting surface facing the circuitsubstrate; attaching a height adjuster including a height adjustmentportion to the optical module such that a lower end of the heightadjustment portion is substantially flush with or lower than thesubstrate mounting surface in the waveguide introduction opening; andfilling a gap between the circuit substrate and the optical modulehaving the height adjuster attached thereto with an underfill material.

The above and other objects, features, advantages and technical andindustrial significance of this invention will be better understood byreading the following detailed description of presently preferredembodiments of the invention, when considered in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view schematically illustrating an opticalmodule according to a first embodiment;

FIG. 2 is an exploded view illustrating the optical module illustratedin FIG. 1;

FIG. 3 is a plan view illustrating the optical module illustrated inFIG. 1;

FIG. 4 is a cross-sectional view taken along the line A-A of FIG. 3;

FIG. 5 is a front view illustrating the optical module illustrated inFIG. 1;

FIG. 6 is a cross-sectional view taken along the line B-B of FIG. 3;

FIG. 7 is a diagram illustrating a method for mounting the opticalmodule on a circuit substrate;

FIG. 8 is a diagram illustrating the optical module mounted on thecircuit substrate;

FIG. 9 is a cross-sectional view schematically illustrating an opticalmodule according to a second embodiment;

FIG. 10 is a diagram illustrating an optical module according to a thirdembodiment and corresponds to the cross-sectional view of FIG. 4;

FIG. 11 is a front view illustrating the optical module according to thethird embodiment;

FIG. 12 is a diagram illustrating the optical module according to thethird embodiment and corresponds to the cross-sectional view of FIG. 6;

FIG. 13 is a diagram illustrating the optical module mounted on acircuit substrate;

FIG. 14 is a cross-sectional view schematically illustrating an opticalmodule according to a fourth embodiment;

FIG. 15 is a plan view schematically illustrating an optical moduleaccording to a fifth embodiment;

FIG. 16 is a diagram illustrating another embodiment of a marker formedon the circuit substrate;

FIG. 17 is a diagram illustrating alignment with the marker illustratedin FIG. 16;

FIG. 18A is a diagram illustrating still another embodiment of themarker formed on the circuit substrate;

FIG. 18B is a diagram illustrating still another embodiment of themarker formed on the circuit substrate;

FIG. 18C is a diagram illustrating still another embodiment of themarker formed on the circuit substrate;

FIG. 18D is a diagram illustrating still another embodiment of themarker formed on the circuit substrate;

FIG. 19 is a diagram illustrating an example of the arrangement of themarkers;

FIG. 20 is a diagram illustrating an example of an optical moduleaccording to another embodiment;

FIG. 21 is a perspective view schematically illustrating a mountingsystem according to a sixth embodiment;

FIG. 22 is a side view of FIG. 21;

FIG. 23 is a front view of FIG. 21;

FIG. 24 is a plan view of FIG. 21;

FIG. 25 is a perspective view illustrating a circuit substrate and asocket illustrated in FIG. 21;

FIG. 26 is a perspective view illustrating an MT connector supportingmember illustrated in FIG. 21;

FIG. 27 is a cross-sectional view illustrating a portion of FIG. 22;

FIG. 28 is a cross-sectional view illustrating a portion of FIG. 23;

FIG. 29A is a diagram illustrating a preferred example of a spacer;

FIG. 29B is a diagram illustrating a preferred example of the spacer;

FIG. 30 is a cross-sectional view illustrating a portion of anevaluation kit according to a seventh embodiment;

FIG. 31 is a diagram schematically illustrating a waveguide supportingmember and an organic optical waveguide illustrated in FIG. 30;

FIG. 32 is a diagram schematically illustrating an opticalmodule-mounted circuit substrate on which an optical module is mountedusing a component of the mounting system;

FIG. 33 is a diagram schematically illustrating an organic opticalwaveguide having a guide hole;

FIG. 34 is a diagram schematically illustrating an opticalmodule-mounted circuit substrate according to an eighth embodiment;

FIG. 35 is a diagram schematically illustrating an opticalmodule-mounted circuit substrate according to a ninth embodiment;

FIG. 36 is a perspective view schematically illustrating an opticalmodule according to a tenth embodiment;

FIG. 37 is a side view schematically illustrating a protector;

FIG. 38 is a diagram illustrating a state in which the protector isattached to the optical module;

FIG. 39 is a diagram schematically illustrating a protector according toanother embodiment;

FIG. 40 is a diagram schematically illustrating a protector according toanother embodiment;

FIG. 41A is a diagram illustrating an aspect in which the optical modulehaving the protector attached thereto is mounted on the circuitsubstrate;

FIG. 41B is a diagram illustrating an aspect in which the optical modulehaving the protector attached thereto is mounted on the circuitsubstrate;

FIG. 42 is a diagram schematically illustrating a protector according tostill another embodiment;

FIG. 43 is a diagram schematically illustrating the protector accordingto still another embodiment;

FIG. 44 is a top view schematically illustrating a height adjuster;

FIG. 45 is a side view schematically illustrating the height adjuster;

FIG. 46 is a diagram illustrating a case in which the height adjuster isnot used;

FIG. 47 is a diagram illustrating a case in which the height adjuster isused;

FIG. 48 is a perspective view schematically illustrating an opticalmodule according to another embodiment to which a protector will beapplied;

FIG. 49 is a cross-sectional view taken along the line C-C of FIG. 48;

FIG. 50 is a perspective view schematically illustrating a protectorwhich can be applied to the optical module illustrated in FIG. 48;

FIG. 51 is a diagram illustrating a state in which the protectorillustrated in FIG. 50 is attached to the optical module illustrated inFIG. 48;

FIG. 52 is a diagram illustrating a state in which the protectorillustrated in FIG. 50 is attached to the optical module illustrated inFIG. 48;

FIG. 53 is a perspective view schematically illustrating a protectoraccording to another embodiment;

FIG. 54 is a diagram illustrating a state in which the protectorillustrated in FIG. 53 is attached to the optical module illustrated inFIG. 48;

FIG. 55 is a diagram illustrating an optical module to which aprotective structure is applied;

FIG. 56 is an exploded view illustrating the optical module illustratedin FIG. 55;

FIG. 57 is a diagram illustrating an optical module to which aprotective structure according to another embodiment is applied;

FIG. 58 is an exploded view illustrating the optical module illustratedin FIG. 57;

FIG. 59A is a perspective view schematically illustrating an opticalmodule according to a modification of the tenth embodiment;

FIG. 59B is a diagram illustrating a state in which the protector isattached to the optical module;

FIG. 59C is a top view illustrating a main portion of FIG. 59B;

FIG. 59D is a cross-sectional view illustrating a main portion takenalong the line D-D of FIG. 59C;

FIG. 59E is a diagram as viewed from an arrow E in FIG. 59C;

FIG. 60 is a diagram illustrating a pin which is formed in a taperedshape;

FIG. 61 is a perspective view schematically illustrating a protectoraccording to still another embodiment;

FIG. 62 is a side view schematically illustrating the protectorillustrated in FIG. 61;

FIG. 63 is a diagram illustrating a state in which the protectorillustrated in FIG. 61 is attached to the optical module illustrated inFIG. 48; and

FIG. 64 is a diagram illustrating a state in which the protectorillustrated in FIG. 61 is attached to the optical module illustrated inFIG. 48.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereafter, embodiments of an optical module, an optical module mountingmethod, an optical module-mounted circuit substrate, an optical moduleevaluation kit system, a circuit substrate, and a communication systemaccording to embodiments of the present invention will be explained withreference to the drawings. The embodiments do not limit the presentinvention. In all the drawings, identical or corresponding elements aregiven same reference numerals. It should be noted that the drawings showschematic examples. Accordingly, a relationship between respectiveelements may be different from real values. Among the drawings, theremay be parts where the relationships and ratios of the shown sizes aredifferent from one another.

In the optical interconnection between the boards, an organic opticalwaveguide made of an organic optical material is expected to be appliedas the optical transmission line. However, since the organic opticalwaveguide is attached onto the circuit substrate, it protrudes from thesurface of the substrate. Therefore, when the organic optical waveguideis mounted on the circuit substrate, there is a concern that the organicoptical waveguide will physically interfere with a housing of an opticalmodule which is optically coupled to the organic optical waveguide.

In contrast, according to the embodiment described below, physicalinterference with an optical waveguide is prevented.

First Embodiment

FIG. 1 is a perspective view schematically illustrating an opticalmodule according to a first embodiment. FIG. 2 is an exploded viewillustrating the optical module illustrated in FIG. 1. FIG. 3 is a planview illustrating the optical module illustrated in FIG. 1. FIG. 4 is across-sectional view taken along the line A-A of FIG. 3. FIG. 5 is afront view illustrating the optical module illustrated in FIG. 1. FIG. 6is a cross-sectional view taken along the line B-B of FIG. 3.Hereinafter, the optical module according to the first embodiment willbe described with reference to FIGS. 1 to 6.

An optical module 100 includes a housing 10, a vertical cavity surfaceemitting laser (VCSEL) array element 20, a driver IC 30, a microlensarray element 40, a lens array element holder 50, and a spacer 60.

The housing 10 includes a rectangular plate member 11 and a U-shapedframe member 12. The plate member 11 has, for example, a stackedsubstrate structure in which five dielectric films, such as five resinfilms, and five copper films forming a wiring pattern are alternatelystacked. The frame member 12 has, for example, a stacked substratestructure in which nine dielectric films, such as nine resin films, andnine copper films forming a wiring pattern are alternately stacked. Theplate member 11 and the frame member 12 are bonded by a bonding layer 13with, for example, solder or Au bumps so as to ensure the electricalconnection between the wiring patterns of the plate member 11 and theframe member 12. The plate member 11 and the frame member 12 are bondedto each other to form an internal space 14, an element mounting surface11 a, and a waveguide introduction opening 15 in the housing 10. Theinternal space 14 includes an opening 14 a which is formed in asubstrate mounting surface 12 a of the frame member 12 opposite to asurface bonded to the plate member 11 and is surrounded by the framemember 12. The element mounting surface 11 a is a portion of the surfaceof the plate member 11 to which the frame member 12 is not bonded andforms a portion of the inner surface of the internal space 14. Thewaveguide introduction opening 15 is formed in a side surface whichintersects the substrate mounting surface 12 a by the opening of theframe member 12 and is connected to the opening 14 a and the internalspace 14.

A marker 11 aa and a concave portion 11 ab for mounting the driver IC 30are formed in the element mounting surface 11 a. A land grid array inwhich planar electrode pads 16 having a diameter of 450 μm are arrangedin a lattice shape at a pitch of, for example, 1 mm is formed on thesubstrate mounting surface 12 a. The planar electrode pads 16 include,for example, a planar electrode pad 16 a for power supply, a planarelectrode pad 16 b for a differential high frequency signal, a planarelectrode pad 16 c for ground, and a planar electrode pad 16 d for acontrol signal. In the drawings, the same type of planar electrode padis hatched in the same manner.

Three guide holes 17 for alignment are formed in the housing 10 so as toextend from the substrate mounting surface 12 a of the frame member 12to a rear surface of the plate member 11 opposite to the substratemounting surface 12 a. The guide holes 17 are arranged so as to form anisosceles triangle in FIG. 3.

The VCSEL array element 20 which is an optical element includes aplurality of (for example, 12) VCSEL elements which are arranged in aone-dimensional array and is mounted in the vicinity of the concaveportion 11 ab of the element mounting surface 11 a. The driver IC 30which is an electronic element is used to drive the VCSEL array element20 and is mounted in the concave portion 11 ab of the element mountingsurface 11 a. The microlens array element 40 is arranged so as tocorrespond to the VCSEL array element 20 and includes, for example, 12microlenses which correspond to the number of VCSEL elements in theVCSEL array element 20 and are arranged in a one-dimensional array. Eachmicrolens in the microlens array element 40 receives a laser opticalsignal output from each VCSEL element, focuses the laser optical signal,and achieves predetermined optical coupling with, for example, anexternal optical component. The microlens array element 40 is made of atranslucent material including glass, such as silica-based glass, or aresin which transmits light emitted from the VCSEL array element.

The lens array element holder 50 holds the microlens array element 40using a holding hole 52 formed in a main surface 51 such that theoptical axis of each microlens in the microlens array element 40 isaligned with the optical axis of each VCSEL element in the VCSEL arrayelement 20. The lens array element holder 50 includes guide holes 53which are formed on both side of the holding hole 52 and function as aguide mechanism for alignment. The use of the guide holes 53 makes itpossible to fit an MT-type optical connector to the optical module 100and to easily test and evaluate the characteristics of the opticalmodule 100. The MT-type optical connector means an optical connector inwhich guide pin holes into which fitting pins can be inserted are formedat both sides of a connection end surface and an optical fiber isarranged between the guide pin holes, like an MT connector defined byJIS C5981. The spacer 60 is interposed between the element mountingsurface 11 a of the plate member 11 and the lens array element holder50. When the thickness of the spacer 60 is changed, the distance betweenthe microlens array element 40 and the VCSEL array element 20 ischanged. Then, the focusing position of the laser light emitted from theVCSEL array element 20 through the microlens array element 40 is alsochanged. This makes it possible to perform correction such that avariation in the distance from the substrate mounting surface 12 a to afocusing point of the microlens array element 40 due to the tolerance ofthe height of the internal space 14 of the housing 10 is reduced. In thelens array element holder 50, a portion of a side surface 54 which facesthe frame member 12 is chamfered so as to be inclined with respect tothe main surface 51. It is preferable that the lens array element holder50 and the spacer 60 be made of a metal material with high thermalconductivity, such as copper.

Next, the operation of the optical module 100 will be described. First,the driver IC 30 is supplied with, for example, a power supply voltagesignal, a differential high frequency signal, and a control signal fromthe outside through the planar electrode pad 16 and the wiring patternformed in the housing 10 and drives the VCSEL array element 20 on thebasis of these signals. Each VCSEL element in the VCSEL array element 20outputs a laser optical signal with a wavelength of, for example, 1.1 μmto 1.5 μm including the differential high frequency signal. Eachmicrolens in the microlens array element 40 receives the laser opticalsignal output from each VCSEL element, focuses the laser optical signal,and achieves predetermined optical coupling with, for example, anexternal optical component. It is preferable to use a lens element, suchas the microlens array element 40, in order to achieve the opticalcoupling. In this case, it is possible to improve coupling efficiency,as compared to so-called butt coupling without using the lens element.

Next, a method for assembling the optical module 100 will be described.First, the plate member 11 and the frame member 12 are bonded to eachother by, for example, solder reflow or Au bump welding. In this case,for example, SnAgCu-based solder having a melting point of about 220° C.is used. In addition, three guide holes 17 can be used for the alignmentbetween the plate member 11 and the frame member 12.

Then, the VCSEL array element 20 is mounted on the element mountingsurface 11 a. It is preferable to use the marker 11 aa for thealignment. In this case, it is possible to mount the VCSEL array element20 at an exact position. Then, the driver IC 30 is mounted in theconcave portion 11 ab of the element mounting surface 11 a. The driverIC 30 is bonded to an electrode pad formed on the element mountingsurface 11 a by a wire. The VCSEL array element 20 and the driver IC 30are bonded to each other by wire bonding. Since the driver IC 30 ismounted in the concave portion 11 ab, the difference in height betweenthe VCSEL array element 20 and the driver IC 30 is reduced. Therefore,it is possible to reduce the length of a bonding wire. As a result, thedeterioration of the quality of the differential high frequency signalwhich is output from the driver IC 30 to the VCSEL array element 20through wire bonding is prevented.

Among the planar electrode pads 16, the planar electrode pad 16 a forpower supply and the planar electrode pad 16 d for a control signal arearranged close to the waveguide introduction opening 15 (U-shapedleading end) of the frame member 12. According to this structure, awiring pattern for a signal other than the differential high frequencysignal is not present on a path from the planar electrode pad 16 b for adifferential high frequency signal to the driver IC 30 through thewiring pattern in the housing 10. Therefore, it is easy to treat awiring pattern for a differential high frequency signal and it ispossible to reduce the length of the pattern and to prevent theinfluence of a low-frequency component of a power supply. As a result,the deterioration of the quality of the differential high frequencysignal is prevented.

Then, the spacer 60 is bonded to the element mounting surface 11 a by,for example, an adhesive. It is preferable that the thickness of theplate member 11 be small in order to reduce the height (thickness) ofthe optical module 100 and thus reduce the size of the optical module100 while ensuring the height of the internal space 14 and in order toeffectively dissipate heat generated during the operation of the driverIC 30. However, when the plate member 11 is too small, there is aconcern that the deformation, such as warpage or flexure, of the platemember 11 will occur due to heat from the driver IC 30. In this case,for example, the distance between the VCSEL array element 20 and themicrolens array element 40 is changed, which may cause the deteriorationof the state of the above-mentioned predetermined optical coupling. Incontrast, when the spacer 60 is made of a material, such as metal with ahigher rigidity than that forming the housing 10, the deformation of theplate member 11 is prevented. Therefore, the deterioration of the stateof the predetermined optical coupling is also prevented.

As described above, since the frame member 12 has the structure in whichdielectrics and copper films are alternately stacked, an error in thethickness of the frame member 12 from the design value is likely tooccur due to, for example, a manufacturing error. When there is an errorin the thickness of the frame member 12, an error in the height of theinternal space 14 also occurs. As a result, an error occurs in thepredetermined optical coupling achieved by the microlens array element40. For this reason, spacers 60 with different thicknesses are preparedin advance and a spacer 60 with a thickness capable of cancelling anerror in the thickness (the height of the internal space 14) of theframe member 12 which has been measured in advance is selected and used.According to this structure, the above-mentioned optical coupling errorproblem is solved.

Then, the microlens array element 40 is inserted into the holding hole52 of the lens array element holder 50 and is then bonded thereto. Then,the lens array element holder 50 is placed on the spacer 60 and theVCSEL array element 20 and the microlens array element 40 are alignedwith each other. Then, the lens array element holder 50 is bonded to thespacer 60. At that time, it is preferable that the gap between the lensarray element holder 50 or the spacer 60 and the driver IC 30 be filledwith a resin with high thermal conductivity, such as silicone. In thiscase, heat generated during the operation of the driver IC 30 isdissipated from the lens array element holder 50 or the spacer 60through the resin.

The alignment between the VCSEL array element 20 and the microlens arrayelement 40 can be performed by a so-called active alignment method whichoperates the VCSEL array element 20 such that laser light is output andobserves the state of light transmitted through the microlens arrayelement 40. In addition, the state of light transmitted through themicrolens array element 40 may be observed by, for example, amicroscope. Alternatively, an MT connector of an optical fiber arraywith a known MT connector may be arranged so as to face the microlensarray element 40 and the intensity of laser light output from theoptical fiber array may be measured. In this embodiment, the MTconnector is used. However, any member having an optical fiber with apositioning structure provided therein can be used. The guide holes 53are provided for alignment with an MT connector for evaluation throughguide pins. In this case, the guide pins are inserted into the guideholes of the MT connector and the guide holes 53 of the lens arrayelement holder 50 to easily fit the MT connector to the lens arrayelement holder 50. At that time, a spacer is inserted between a lightinput/output end surface of an organic waveguide and the MT connectorsuch that light is coupled to an optical connection end surface of theMT connector. According to this structure, it is possible to accuratelyalign the MT connector with the microlens array element 40 and to easilyevaluate the characteristics of the optical module 100. Therefore,active alignment with high positioning accuracy is achieved.

As described above, in the lens array element holder 50, a portion ofthe side surface 54 which faces the frame member 12 is chamfered.Therefore, an adhesive for bonding the lens array element holder 50 tothe spacer 60 is likely to flow into the holding hole and workability isimproved.

Then, a method for mounting the optical module 100 on a circuitsubstrate will be described. FIG. 7 is a diagram illustrating the methodfor mounting the optical module on the circuit substrate. As illustratedin FIG. 7, an organic optical waveguide 210 is mounted on a circuitsubstrate 200 by adhesion. One end of the organic optical waveguide 210is processed into a wedge portion 211. In addition, three markers 220which are arranged so as to correspond to the arrangement of the guideholes 17 in the optical module 100 are provided on the circuit substrate200.

For example, a known flip-chip bonder can be used to mount the opticalmodule 100 on the circuit substrate 200. In this case, the rear surface11 b of the optical module 100 is sucked and lifted by the head of theflip-chip bonder and the optical module 100 is moved and placed at apredetermined position on the circuit substrate 200. Then, heat isapplied from the head through the housing 10 to solder each planarelectrode pad 16 of the optical module 100 to each electrode pad of thecircuit substrate 200. In this way, a circuit substrate 1000 having theoptical module 100 mounted thereon is completed.

During the mounting, the substrate mounting surface 12 a of the opticalmodule 100 faces the circuit substrate 200 and the alignment between theguide holes 17 and the markers 220 on the circuit substrate 200 isperformed while the markers 220 on the circuit substrate 200 areobserved through the guide holes 17 of the optical module 100. In thisway, it is possible to accurately mount the optical module 100 at adesired position on the circuit substrate 200.

In particular, in the first embodiment, since the three guide holes 17are aligned with the three markers 220, it is easy to check thepositional deviation of the optical module 100 in the rotation directionand the amount of deviation of the optical module 100 and to correct thepositional deviation. Therefore, it is easier to accurately mount theoptical module 100 at a desired position on the circuit substrate 200with high positioning accuracy. In this embodiment, the three guideholes 17 and the three markers 220 are arranged so as to form anisosceles triangle. However, they may be arranged so as to form othertriangles.

The organic optical waveguide 210 protrudes from the surface of thecircuit substrate 200. When the optical module 100 is mounted on thecircuit substrate 200, the organic optical waveguide 210 is introducedinto the internal space 14 through the waveguide introduction opening15. Therefore, it is possible to prevent the physical interferencebetween the organic optical waveguide 210 and the optical module 100.

When the flip-chip bonder is used for mounting, it is preferable to uselow-melting-point solder with a lower melting point thanhigh-melting-point solder for bonding the plate member 11 and the framemember 12 such that the high-melting-point solder is not melted by heatapplied from the head. Examples of the low-melting-point solder includeSnAgCu-based solder with a melting point of about 220° C., SnPb-basedsolder with a melting point of about 183° C., and SnBi-based solder witha melting point of about 137° C. However, even when SnAgCu solder isused to bond the frame member and the plate member, the melting point ofthe solder increases after the solder is melted. When the temperature isaccurately managed during the mounting of the optical module, it is alsopossible to use SnAgCu-based solder. In addition, it is preferable thatthe microlens array element 40 be made of glass. In this case, even whenheat is applied from the flip-chip bonder in order to mount the opticalmodule, deformation caused by heat is less likely to occur. In addition,it is preferable that an adhesive used to bond the microlens arrayelement 40, the lens array element holder 50, or the spacer 60 be madeof, for example, an epoxy resin with high heat resistance.

FIG. 8 is a diagram illustrating the optical module mounted on thecircuit substrate. As illustrated in FIG. 8, the VCSEL array element 20is electrically connected to the driver IC 30 by a bonding wire 101. Thedriver IC 30 is electrically connected to the electrode pad (notillustrated) on the element mounting surface 11 a by a bonding wire 102.The electrode pad is electrically connected from the wiring patternformed on the element mounting surface 11 a to the wiring pattern on thecircuit substrate 200 through the plate member 11, the bonding layer 13,the frame member 12, and each planar electrode pad 16, as represented byan electrical path DL.

The alignment between the guide holes 17 in the optical module 100 andthe markers 220 on the circuit substrate 200 is performed to align theVCSEL element with the guide hole 17 of the optical module 100 and toalign the markers 220 on the circuit substrate 200 with the organicoptical waveguide 210. Therefore, the optical module 100 is mounted suchthat the exact positional relationship between the microlens arrayelement 40 and the organic optical waveguide 210 is established.

Since the organic optical waveguide 210 is introduced into the internalspace 14 through the waveguide introduction opening 15, the organicoptical waveguide 210 does not physically interfere with the opticalmodule 100. The thickness of the frame member 12 is appropriately set toprevent the physical interference between the organic optical waveguide210 and the microlens array element 40 and between the organic opticalwaveguide 210 and the lens array element holder 50. In this case, thewaveguide introduction opening 15 may be closed with, for example,grease or a resin such that dust does not get into the internal space14.

When the optical module 100 is used, the driver IC 30 is supplied with,for example, the power supply voltage signal, the differential highfrequency signal, and the control signal from the circuit substrate 200through the planar electrode pads 16. The VCSEL array element 20 isdriven by the driver IC 30. Each VCSEL element outputs a laser opticalsignal L including the differential high frequency signal. Eachmicrolens of the microlens array element 40 receives the laser opticalsignal L output from each VCSEL element and focuses the laser opticalsignal L on the organic optical waveguide 210 from the upper side of theorganic optical waveguide 210. The wedge portion 211 reflects thefocused laser optical signal L so as to be coupled to the organicoptical waveguide 210. The organic optical waveguide 210 transmits thelaser optical signal L to, for example, another circuit substrate.

As described above, the spacer 60 has the effect of preventing thedeformation of the plate member 11 and the effect of reducing avariation in the distance from the substrate mounting surface 12 a tothe focusing point of the microlens array element 40 due to thetolerance of the thickness of the frame member 12. Therefore, the propercoupling of the laser optical signal L to the organic optical waveguide210 is obtained by the spacer 60.

In this embodiment, instead of the VCSEL array element 20, a photodiodearray element which is a light receiving element and has substantiallythe same structure as the optical module 100 is mounted on the circuitsubstrate 200. In addition, instead of the driver IC 30, an opticalmodule for reception which has, for example, a trans-impedance amplifieror a limiting amplifier mounted thereon is mounted on the circuitsubstrate 200. The optical module for reception can receive a laseroptical signal which is transmitted from another circuit substratethrough another organic optical waveguide. In this way, boards areoptically interconnected.

As described above, according to the optical module 100 of the firstembodiment, the physical interference between the optical module 100 andthe organic optical waveguide 210 is prevented. In addition, it is easyto accurately mount the optical module 100 at a desired position on thecircuit substrate 200 with high positioning accuracy. Therefore, it ispossible to easily align the optical axis of the VCSEL array element 20with the optical axis of the organic optical waveguide 210 with highaccuracy. As a result, it is easy to obtain the proper optical couplingbetween the laser optical signal L output from the VCSEL array element20 and the organic optical waveguide 210.

Second Embodiment

FIG. 9 is a cross-sectional view schematically illustrating an opticalmodule according to a second embodiment of the invention. As illustratedin FIG. 9, an optical module 100A according to the second embodimentdiffers from the optical module 100 according to the first embodiment inthat a housing 10A replaces the housing 10 in the optical module 100.The housing 10A differs from the housing 10 in that a plate member 11Areplaces the plate member 11 in the housing 10.

The plate member 11A differs from the plate member 11 in that aplurality of rod-shaped radiation members 71 are provided so as to passthrough the plate member 11A from the bottom of the concave portion 11ab on the rear surface side of the driver IC 30. The radiation member 71is made of a material with high thermal conductivity and is preferablymade of, for example, copper or aluminum. In addition, a heat sink 72 isprovided on the rear surface 11 b of the plate member 11A so as to comeinto contact with the radiation members 71. The heat sink 72 is alsomade of a material with high thermal conductivity and is preferably madeof, for example, copper or aluminum.

In the optical module 100A, the radiation members 71 and the heat sink72 dissipate heat generated during the operation of the driver IC 30,which is further preferable. In addition, via holes are formed in theplate member 11A and the radiation members 71 with high thermalconductivity are inserted into the via holes.

A mounting method using solder will be described as another example ofthe method for mounting the optical module.

In general, the optical module 100 has a ball grid array (BGA) in whichsolder balls are provided on the planar electrode pads 16 on the surface(substrate mounting surface 12 a) of the optical module 100 having theplanar electrode pads 16 formed thereon in the first stage in which theoptical module 100 is manufactured or after the optical module 100 ismanufactured. Then, the solder is melted to mount the optical module 100on a circuit substrate (Opto-substrate).

However, in this embodiment, as in the drawing, the planar electrodepads 16 of the optical module 100 are arranged in a land grid array(LGA) and the optical module 100 is mounted by a method without using asolder ball.

Specifically, a mask plate with a thickness of about 10 μm in which ahole for electrical connection is formed at a predetermined position isplaced on the Opto-substrate. Then, a solder cream is applied onto themask plate and is then uniformly spread so as to get into the hole. Inaddition, the extra solder cream thicker than the mask plate is removed.In this way, a solder cream layer with a thickness of about 100 μm isformed at a predetermined position for electrical connection.

Then, the optical module 100 and the Opto-substrate are aligned witheach other and the solder is melted to mount the optical module 100 onthe Opto-substrate. For example, a mounting method with a flip-chipbonder or a reflow mounting method with a reflow furnace is used as themounting method.

Then, the gap of the mounting surface is filled with a general underfillmaterial such as a resin material.

The solder cream layer which has a thickness of about 100 μm and isformed at a predetermined position for electrical connection may beformed on the optical module.

It was confirmed that the object (the Opto-substrate having the opticalmodule mounted thereon) soldered by the method without using a solderball did not have a reliability problem.

When the above-mentioned mounting method is used, it is possible toreduce the thickness of the solder layer, as compared to the BGA.Therefore, it is possible to reduce a variation in the distance betweenthe frame member and the circuit substrate. As a result, it is possibleto stably couple light output from the optical module to the organicoptical waveguide.

In the above-described embodiment, the housing is formed by bonding theplate member and the frame member. However, the invention is not limitedthereto. The housing may have any structure as long as it has theopening, the internal space, the waveguide introduction opening. Forexample, the plate member and the frame member may be integrated witheach other to form the housing. It is preferable that the housing have aU-shape. In this case, an area capable of arranging the LGA is large. Inaddition, the plate member is not limited to the rectangular shape. Theframe member is not limited to the U shape in which one side of therectangular frame is entirely opened, as described in theabove-described embodiment. For example, the frame member may have ashape in which only a portion of one side of the frame is opened or someor all of a plurality of sides are opened.

Third Embodiment

FIG. 10 is a diagram which illustrates an optical module according to athird embodiment of the invention and corresponds to the cross-sectionalview of FIG. 4. FIG. 11 is a front view illustrating the optical moduleaccording to the third embodiment. FIG. 12 is a diagram whichillustrates the optical module according to the third embodiment of theinvention and corresponds to the cross-sectional view of FIG. 6. FIG. 13is a diagram illustrating the optical module mounted on a circuitsubstrate.

As illustrated in FIGS. 10 to 13, an optical module 100B according tothe third embodiment differs from the optical module 100 according tothe first embodiment in that a bonding layer 13B replaces the bondinglayer 13 in the optical module 100.

The plate member 11 and the frame member 12 are bonded to each other bya metal bonding material 13Ba serving as a first bonding material, suchas solder, an Au bump, or a conductive resin, and a resin adhesive 13Bbserving as a second bonding material which is provided so as to fill agap between the metal bonding materials 13Ba, in the bonding layer 13Bso as to connect the wiring patterns of the plate member 11 and theframe member 12 and to ensure the electrical connection thereof.

The optical module 100B has the same operation as the optical module100.

Next, a method for assembling the optical module 100B will be described.First, the plate member 11 and the frame member 12 are bonded to eachother. The bonding is performed by a plurality of metal bondingmaterials 13Ba and the resin adhesive 13Bb which is provided so as tofill the gap between the metal bonding materials 13Ba. The metal bondingmaterial 13Ba is bonded by, for example, solder reflow or Au bumpwelding. In this case, for example, SnAgCu-based solder having a meltingpoint of about 220° C. is used. Alternatively, for example, solder inwhich a re-melting temperature after reflow is higher than a meltingtemperature during reflow, such as solder using metal nanoparticlepaste, may be used. In addition, the alignment between the plate member11 and the frame member 12 can be performed using three guide holes 17.

It is preferable that the thickness of the plate member 11 be small inorder to reduce the height (thickness) of the optical module 100B andthus reduce the size of the optical module 100B while ensuring theheight of the internal space 14 and in order to effectively dissipateheat generated during the operation of the driver IC 30. However, whenthe plate member 11 is too thin, there is a concern that the mechanicalstrength of the plate member 11 will not be ensured. As a result, thereis a concern that the deformation, such as warpage or flexure, of theplate member 11 will occur due to heat from the driver IC 30. In thiscase, for example, the distance between the VCSEL array element 20 andthe microlens array element 40 is changed, which may cause thedeterioration of the state of the above-mentioned predetermined opticalcoupling. However, in the third embodiment, the plate member 11 and theframe member 12 are bonded to each other by not only the metal bondingmaterials 13Ba, but also the resin adhesive 13Bb which is provided so asto fill the gap between the metal bonding materials 13Ba. Therefore, thebonding area between the plate member 11 and the frame member 12increases. Even when the plate member 11 is thin, the insufficientmechanical strength of the plate member 11 is supplemented and thedeformation of the plate member 11 is prevented. In addition, since thebonding area between the plate member 11 and the frame member 12 islarge, the radiation performance is further improved.

Then, the VCSEL array element 20 is mounted on the element mountingsurface 11 a. It is preferable to use the marker 11 aa for alignment. Inthis case, it is possible to mount the VCSEL array element 20 at anexact position. Then, the driver IC 30 is mounted in the concave portion11 ab of the element mounting surface 11 a. The driver IC 30 is bondedto an electrode pad formed on the element mounting surface 11 a by awire. The VCSEL array element 20 and the driver IC 30 are bonded to eachother by wire bonding. Since the driver IC 30 is mounted in the concaveportion 11 ab, a difference in height between the VCSEL array element 20and the driver IC 30 is reduced. Therefore, it is possible to reduce thelength of a bonding wire. As a result, the deterioration of the qualityof a differential high frequency signal which is output from the driverIC 30 to the VCSEL array element 20 through wire bonding is prevented.In addition, since the thickness of the plate member 11 at the concaveportion 11 ab is small, the radiation performance is improved.

Among the planar electrode pads 16, the planar electrode pad 16 a forpower supply and the planar electrode pad 16 d for a control signal arearranged close to the waveguide introduction opening 15 (U-shapedleading end) of the frame member 12. According to this structure, awiring pattern for a signal other than the differential high frequencysignal is not present on a path from the planar electrode pad 16 b for adifferential high frequency signal to the driver IC 30 through thewiring pattern in the housing 10. Therefore, it is easy to treat awiring pattern for a differential high frequency signal and it ispossible to reduce the length of the pattern and to prevent theinfluence of a low-frequency component of a power supply. As a result,the deterioration of the quality of the differential high frequencysignal is prevented.

Then, the spacer 60 is bonded to the element mounting surface 11 a by,for example, an adhesive. When the spacer 60 is made of a material, suchas metal, having a higher rigidity than that forming the housing 10, theinsufficient mechanical strength of the plate member 11 is supplementedand the deformation of the plate member 11 is prevented. Therefore, thedeterioration of the state of the predetermined optical coupling isprevented.

As described above, since the frame member 12 has the structure in whichdielectrics and copper films are alternately stacked, an error in thethickness of the frame member 12 from the design value is likely tooccur due to, for example, a manufacturing error. When there is an errorin the thickness of the frame member 12, an error in the height of theinternal space 14 also occurs. As a result, an error occurs in thepredetermined optical coupling achieved by the microlens array element40. For this reason, the spacers 60 with different thicknesses areprepared in advance and a spacer 60 with a thickness capable ofcancelling an error in the thickness (the height of the internal space14) of the frame member 12 which has been measured in advance isselected and used. According to this structure, the above-mentionedoptical coupling error problem is solved.

Then, the microlens array element 40 is inserted into the holding hole52 of the lens array element holder 50 and is then bonded thereto. Then,the lens array element holder 50 is placed on the spacer 60 and theVCSEL array element 20 and the microlens array element 40 are alignedwith each other. Then, the lens array element holder 50 is bonded to thespacer 60. At that time, it is preferable that the gap between the lensarray element holder 50 or the spacer 60 and the driver IC 30 be filledwith a resin with high thermal conductivity, such as silicone. In thiscase, heat generated during the operation of the driver IC 30 isdissipated from the lens array element holder 50 or the spacer 60through the resin.

The alignment between the VCSEL array element 20 and the microlens arrayelement 40 can be performed by a so-called active alignment method whichoperates the VCSEL array element 20 such that laser light is output andobserves the state of light transmitted through the microlens arrayelement 40. In addition, the state of light transmitted through themicrolens array element 40 may be observed by, for example, amicroscope. Alternatively, an MT connector of an optical fiber arraywith a known MT connector may be arranged so as to face the microlensarray element 40 and the intensity of laser light output from theoptical fiber array may be measured. In this embodiment, the MTconnector is used. The guide holes 53 are formed so as to be fitted toan MT connector for evaluation through guide pins and are provided foralignment. In this case, the guide pins are inserted into the guideholes of the MT connector and the guide holes 53 of the lens arrayelement holder 50 to easily fit the MT connector to the lens arrayelement holder 50. At that time, a spacer is inserted between a lightinput/output end surface of an organic optical waveguide and the MTconnector such that light is coupled to an optical connection endsurface of the MT connector. According to this structure, it is possibleto accurately align the MT connector with the microlens array element 40and to easily evaluate the characteristics of the optical module 100B.Therefore, active alignment with high positioning accuracy is achieved.

As described above, in the lens array element holder 50, a portion ofthe side surface 54 which faces the frame member 12 is chamfered.Therefore, an adhesive for bonding the lens array element holder 50 tothe spacer 60 is likely to flow into the holding hole and workability isimproved.

For example, a known flip-chip bonder can be used to mount the opticalmodule 100B on the circuit substrate 200.

When the flip-chip bonder is used for mounting, it is preferable to uselow-melting-point solder with a lower melting point thanhigh-melting-point solder such that the metal bonding material 13Babonding the plate member 11 and the frame member 12, for example, thehigh-melting-point solder is not melted by heat applied from the head.Examples of the low-melting-point solder include SnAgCu-based solderwith a melting point of about 220° C., SnPb-based solder with a meltingpoint of about 183° C., and SnBi-based solder with a melting point ofabout 137° C. However, even when SnAgCu solder is used to bond the framemember and the plate member, the melting point of the solder increasesafter the solder is melted. Therefore, when the temperature isaccurately managed during the mounting of the optical module, it is alsopossible to use SnAgCu-based solder. In addition, it is preferable thatthe microlens array element 40 be made of glass. In this case, even whenheat is applied from the flip-chip bonder in order to mount the opticalmodule, deformation caused by heat is less likely to occur. In addition,it is preferable that an adhesive used to bond the microlens arrayelement 40, the lens array element holder 50, or the spacer 60 be madeof, for example, an epoxy resin with high heat resistance.

However, even when the metal bonding material 13Ba bonding the platemember 11 and the frame member 12 is melted by mounting with theflip-chip bonder or heat generated from the driver IC 30, the bondingbetween the plate member 11 and the frame member 12 may be maintained bythe resin adhesive 13Bb such that resistance to welding pressure whichis applied to the housing 10 during mounting is obtained. From thispoint of view, it is preferable that the resin adhesive 13Bb be made ofa material which is less likely to be deformed by heat than the metalbonding material 13Ba. A material with high heat resistance, such as anepoxy resin, can be used as an example of the resin adhesive 13Bb. Inaddition, when it is not mixed with the metal bonding material 13Bawhich is used for electrical connection, it may be made of a materialwith insulating properties.

FIG. 13 is a diagram illustrating the optical module mounted on thecircuit substrate. As illustrated in FIG. 13, the VCSEL array element 20is electrically connected to the driver IC 30 by a bonding wire 101. Thedriver IC 30 is electrically connected to an electrode pad (notillustrated) on the element mounting surface 11 a by a bonding wire 102.The electrode pad is electrically connected from the wiring patternformed on the element mounting surface 11 a to the wiring pattern on thecircuit substrate 200 through the plate member 11, the bonding layer13B, the frame member 12, and each planar electrode pad 16, asrepresented by an electrical path DL.

According to the optical module 100B of the third embodiment, eventhough the thickness of the plate member 11 is small, the deformation ofthe plate member 11 is suppressed. Therefore, a reduction in the size ofthe optical module 100B and a high radiation performance are achievedwhile the sufficient strength of the housing is ensured. In addition,the proper optical coupling between the laser optical signal L outputfrom the VCSEL array element 20 and the organic optical waveguide 210 isachieved.

Fourth Embodiment

FIG. 14 is a cross-sectional view schematically illustrating an opticalmodule according to a fourth embodiment of the invention. As illustratedin FIG. 14, an optical module 100C according to the fourth embodimentdiffers from the optical module 100B according to the third embodimentin that the housing 10A replaces the housing 10 in the optical module100B. The housing 10A differs from the housing 10 in that the platemember 11A replaces the plate member 11 and a supporting member 73 isinserted into the guide hole 17 in the housing 10.

The plate member 11A differs from the plate member 11 in that theplurality of rod-shaped radiation members 71 are provided so as to passthrough the plate member 11A from the bottom of a concave portion 11 abon the rear surface side of the driver IC 30. The radiation member 71 ismade of a material with high thermal conductivity and is preferably madeof, for example, copper or aluminum. In addition, the heat sink 72 isprovided on the rear surface 11 b of the plate member 11A so as to comeinto contact with the radiation members 71. The heat sink 72 is alsomade of a material with high thermal conductivity and is preferably madeof, for example, copper or aluminum.

The supporting member 73 is made of metal, such as copper or aluminum,and is inserted into the guide hole 17 to further improve the mechanicalstrength of the housing 10A. It is preferable that the supporting member73 be inserted into the guide hole 17 by press fitting or fixed to theguide hole 17 by, for example, an adhesive. In this case, it is possibleto further improve the mechanical strength of the housing 10A.

In the optical module 100C, heat generated during the operation of thedriver IC 30 is dissipated by the radiation members 71 and the heat sink72, which is further preferable. In addition, instead of burying theradiation members 71 in the plate member 11A, via holes may be formed inthe plate member 11A and the radiation members 71 with high thermalconductivity may be inserted into the via holes. In addition, as astructure which brings the supporting member 73 into contact with thecircuit substrate, heat generated from the optical module 100C may bedissipated to the circuit substrate through the supporting member 73.

Alternatively, the lens array element holder 50 and the circuitsubstrate may be thermally connected to each other by, for example, athermally conductive resin to dissipate heat.

In the above-described embodiment, the resin adhesive is used as thesecond bonding material. However, instead of the resin adhesive, forexample, an adhesive plate member having an adhesive applied thereon maybe provided so as to fill the gap between the first bonding materials.

For example, the supporting member 73 according to the fourth embodimentmay be applied to other embodiments. Since the strength of the housingis ensured, for example, other elements may be further mounted on theoptical module according to each embodiment. In this case, thedeformation of the housing is suppressed even though pressure is appliedto the housing during the flip-chip bonding of other elements.

Fifth Embodiment

FIG. 15 is a plan view schematically illustrating an optical moduleaccording to a fifth embodiment of the invention. The optical moduleaccording to the fifth embodiment illustrated in FIG. 15 differs fromthe optical module 100 according to the first embodiment in that opticalmembers 18 are provided in each of the three guide holes 17. Eachoptical member 18 is, for example, an optical window or a lens. Eachoptical member 18 may be inserted into each guide hole 17 or may beprovided so as to cover each guide hole 17.

In particular, when the optical member 18 is a lens, the followingeffect is obtained. That is, when the optical module is inclined withrespect to the circuit substrate, the distances between the lenses andmarkers on the circuit substrate are different from each other.Therefore, when the markers on the circuit substrate are observed fromthe guide holes 17 through the lenses, the markers with the same sizelook to have different sizes. Therefore, it is possible to easily checkthe deviation of the optical module in the vertical direction. Inaddition, when the inclination of the optical module is adjusted suchthat the markers look to have the same size, it is possible toaccurately mount the optical module.

In each embodiment, as illustrated in FIG. 15, one side S of anisosceles triangle formed by the guide holes 17 is substantiallyparallel to the arrangement direction D of unit elements (VCSEL elementsor microlenses) of the microlens array element 40 and the VCSEL arrayelement 20 provided below the microlens array element 40. As such, whenthe VCSEL array element 20 and the microlens array element 40 aremounted such that the direction of the side S is substantially parallelto the arrangement direction D, the accuracy of mounting is improvedand, particularly, a variation in the optical coupling state of eachunit element is suppressed, which is preferable.

In the fifth embodiment, the optical member 18 is provided in each ofthe three guide holes 17. However, the optical member 18 may be providedin at least one of the three guide holes 17.

Other Embodiments of Marker

Next, other embodiments of the marker formed on the circuit substratewill be described. FIG. 16 is a diagram illustrating another embodimentof the marker formed on the circuit substrate. In the embodimentillustrated in FIG. 16, three markers 220A which are formed byconcentrically arranging three triangles with different sizes are formedon a circuit substrate 200A. One of the vertexes of each marker 220Afaces the center of gravity of the three markers 220A.

FIG. 17 is a diagram illustrating alignment with the markers illustratedin FIG. 16. Letter V indicates the range of the field of view when thecircuit substrate 200A is seen through the guide hole 17. For example,each of the optical modules 100 and 100A to 100C according to theabove-described embodiments is mounted on the circuit substrate 200A asfollows. That is, the deviation of the circuit substrate 200A in arotation direction Ar1 or a plane direction Ar2 is adjusted, on thebasis of the shape or direction of the marker 220A which is seen in thefield of view V from the guide hole 17, such that the aspects of themarkers 220A seen in the field of view V are the same, thereby aligning,for example, the optical module 100 with the circuit substrate 200A.Therefore, mounting is performed with high positioning accuracy. InFIGS. 16 and 17, one of the vertexes of each marker 220A faces thecenter of gravity of the three markers 220A. However, one of the sidesof each marker 220A may face the center of gravity of the three markers220A.

FIGS. 18A to 18D are diagrams illustrating other embodiments of themarker mounted on the circuit substrate. FIG. 18A illustrates a markerformed by a single triangle or circular. FIG. 18B illustrates a markerwhich is formed by concentrically arranging three triangles or circleswith different sizes. FIG. 18C illustrates a marker which is formed byeccentrically arranging three triangles or circles with different sizesfrom a concentric position in a predetermined direction. FIG. 18Dillustrates a marker which is formed by concentrically arranging fourtriangles or circles with different sizes. As such, the number oftriangles or circles arranged is not particularly limited. In eachmarker illustrated in FIG. 18D, the gap between the triangles or thecircles is smaller than the width of the field of view V through theguide hole. According to this structure, it is possible tosimultaneously observe a plurality of triangles or circles. Therefore,it is easy to check the direction of the positional deviation betweenthe optical module and the circuit substrate and to align the opticalmodule and the circuit substrate.

FIG. 19 is a diagram illustrating an example of the arrangement of themarkers. In FIG. 19, the eccentric direction of a marker 220Billustrated in FIG. 18C which is formed by three eccentric circles isaligned with the direction of the center of gravity G of the threemarkers 220B. Therefore, it is easy to check the direction of thepositional deviation between the optical module and the circuitsubstrate and to align the optical module and the circuit substrate.

In the above-described embodiment, the marker is formed by circles ortriangles. However, the marker may be formed by other geometric figures,such as a cross and a polygon. In addition, the guide hole and themarker may have the same shape. When a plurality of geometric figureswith different sizes are arranged to form a marker, a vernier scale isformed in any optical window. In this case, it is possible to accuratelycheck the amount of positional deviation between the optical module andthe circuit substrate. As a result, it is possible to accurately alignthe optical module and the circuit substrate.

In addition, for example, a CCD camera is mounted on a flip-chip bonderand captures the image of the shape of the marker seen through the guidehole. Then, the shape of the marker is compared with the variouspatterns of the positional relationship which have been stored in amemory in advance and a mounting position is corrected on the basis ofthe comparison result. According to this structure, it is possible toautomate a mounting operation and to improve manufacturability.

For example, other elements, or one or more substrates having otherelements mounted thereon may be stacked on the optical module accordingto each embodiment. The stacking of the substrates is implemented by,for example, a POP mounting method. In this case, other elements orother substrates can be accurately mounted by the guide holes which areprovided so as to pass through the housing.

Sixth Embodiment

Next, an example of an optical module mounting system (hereinafter,referred to as a mounting system) according to a sixth embodiment of theinvention will be described.

For example, the optical module 100 according to the first embodiment ismounted on the optical module mounting system according to the sixthembodiment. However, any of the optical modules according to the secondto fifth embodiments may be mounted on the optical module mountingsystem.

FIG. 20 illustrates an example of another optical module mounted on theoptical module mounting system according to the sixth embodiment. InFIG. 20, reference numeral 100D indicates an optical module, referencenumeral 10D indicates a package, reference numeral 19A indicates awaveguide (optical fiber), reference numeral 19B indicates an opticalelement, and reference numeral 19C indicates an optical connector. Inthis embodiment, the waveguide 19A is an optical fiber which is bent atan angle of 90 degrees. However, an optical path may be bent by, forexample, a 90-degree bending mirror. In the optical module 100D, the90-degree bending optical connector 19C and the package 10D are fixed byan adhesive R so as to be optically connected to each other.

Next, the optical module mounting system according to the invention willbe described. FIG. 21 is a perspective view schematically illustratingthe mounting system according to the sixth embodiment. FIGS. 22, 23, and24 are a side view, a front view, and a plan view of FIG. 21,respectively.

As illustrated in FIGS. 21 to 24, a mounting system 2000 includes acircuit substrate 300 including an electronic component for operating,for example, an optical module, a socket 400, a cover 500, and an MTconnector supporting member 600. FIG. 25 is a perspective viewillustrating the circuit substrate 300 and the socket 400. FIG. 26 is aperspective view illustrating the MT connector supporting member 600.FIG. 27 is a cross-sectional view illustrating a portion of FIG. 22.FIG. 28 is a cross-sectional view illustrating a portion of FIG. 23. Asillustrated in FIGS. 27 and 28, the mounting system 2000 furtherincludes a spacer 700. The spacer 700 is made of metal with rigiditysuch as copper.

The circuit substrate 300 includes a wiring pattern 301 which is formedon a main surface and supplies power and an electric signal for drivingthe optical module 100 to the optical module 100 and an insertion hole302 that is an opening which is formed on the main surface and intowhich an MT connector C is inserted (see FIGS. 27 and 28).

The socket 400 is a frame which is placed on the circuit substrate 300so as to accommodate the optical module 100 and includes an opening 401,a mounting portion 402 for mounting the optical module 100, and fourscrew portions 403 which are inserted into through holes provided in thecircuit substrate 300. The mounting portion 402 is made of a dielectric,for example, a resin such as polyetherimide. A pin 402 a with a spring,which is a conductive member for ensuring electrical connection to thewiring pattern 301 of the circuit substrate 300, is provided as aninterface in the mounting portion 402 (see FIGS. 27 and 28).

The cover 500 includes four coil springs 502 which are provided in aninternal space 501 of a cover body, a pressing plate 503 which isprovided at the leading ends of the springs 502, two latch structures504 which are provided on the front side, and coil springs 505 whichurges the latch structures 504. The latch structures 504 urged by thesprings 505 are fitted to the socket 400 and the cover 500 is locked tothe socket 400. The springs 502 and the pressing plate 503 form apressing mechanism.

The MT connector supporting member 600 includes four supporting pillars601 that protrude from a plate-shaped body and are made of an elasticmaterial such as rubber, an MT connector supporting hole 602 thatsupports an MT connector C which is a light receiving member (opticalcoupling member) to be optically coupled with the optical module 100, anopening 603 for introducing the MT connector C into the MT connectorsupporting hole 602, and nuts 604. A through hole 601 a is provided inthe supporting pillar 601. At that time, the opening 603 may have awidth, a size, and a shape capable of introducing an optical fiber tapeconnected to the MT connector C, in order to introduce the MT connectorC from the side. In this embodiment, an elastic member is used as thesupporting pillar 601. However, instead of this structure, a structuremay be used in which, for example, a spring is inserted between the MTconnector supporting member 600 and the circuit substrate.

The MT connector supporting member 600 is provided on a surface of thecircuit substrate 300 opposite to the socket 400. The socket 400 and theMT connector supporting member 600 are fixed to the circuit substrate300 as follows. The MT connector C is introduced into the MT connectorsupporting hole 602 through the opening 603 and the circuit substrate300 is interposed between the socket 400 and the MT connector supportingmember 600. In this state, the screw portions 403 of the socket 400 areinserted into the through holes 601 a of the supporting pillar 601 andthe nuts 604 are threadably engaged with the screw portions 403.

The MT connector C is connected to an external device.

A step portion 602 a is provided in the MT connector supporting hole 602(see FIGS. 26 and 27). When the MT connector C is introduced into the MTconnector supporting hole 602 through the opening 603, at least aportion of an end portion opposite to an optical connection end surfaceof the MT connector C is placed on the step portion 602 a. The movementof the MT connector C in the lower direction (a direction in which theMT connector C becomes further away from the optical module) isregulated by the step portion 602 a.

A spacer 700 which is slightly lower than the supporting pillar 601 isinterposed between the MT connector supporting member 600 and thecircuit substrate 300, with the MT connector C inserted into aninsertion hole 701 of the spacer 700 (the nuts 604 are tightened to makethe height of the supporting pillar 601 substantially equal to that ofthe spacer). The spacer 700 and a thick chin portion of the MT connectorC are fitted to regulate the movement of the MT connector C in the upperdirection. Therefore, the movement of the MT connector C in the upperand lower directions is regulated by the step portion 602 a and thespacer 700. The MT connector supporting member 600 and the spacer 700form a mechanism for positioning the MT connector C, which is a lightreceiving member, in the height direction. That is, for the positioningof the optical module and the MT connector in the optical axis directionduring the optical coupling between the optical module and the MTconnector, the position of the MT connector C is set relative to thecircuit substrate. At that time, positioning in the vertical directionis performed by the MT connector supporting member 600 and the spacer700. However, when the size of the insertion hole 302 is determined, theoptical axis in the horizontal direction may be adjusted such that aslight clearance is formed in the lateral direction.

FIGS. 29A and 29B illustrate a preferred example of the spacer. A spacer700A includes a guide portion 703 and a plate portion 702. The guideportion 703 regulates the insertion of the MT connector C. The plateportion 702 comes into surface contact with the circuit substrate 300.The size of the insertion hole 302 may be 0.5 mm to 1 mm greater thanthe outer size of the guide portion 703. In this case, the MT connectorC can be moved in the plane and it is easy to perform alignment in thehorizontal direction. In addition, the plate portion 702 may have, forexample, a rectangular shape, a square shape, or an elliptical shape. Inaddition, the shape of the insertion hole 302 and the guide portion 703is not limited to this embodiment and can be appropriately set.

An example of a process of mounting the optical module 100 on themounting system 2000 will be described. First, the socket 400 is placedon the circuit substrate 300. Then, the MT connector C is introducedinto the MT connector supporting hole 602 through the opening 603 of theMT connector supporting hole 602. Then, the MT connector C is insertedinto the insertion hole 701 of the spacer 700 and the spacer 700 isinterposed between the MT connector supporting member 600 and thecircuit substrate 300. In this state, the nuts 604 are threadablyengaged with the screw portions 403 of the socket 400 to fix the socket400 and the MT connector supporting member 600 to the circuit substrate300.

Then, the optical module 100 is placed on the mounting portion 402 suchthat the substrate mounting surface 12 a comes into contact with themounting portion 402 and is accommodated in the socket 400. Then, guidepin holes C1 of the MT connector C and the guide holes 53 of the opticalmodule 100 are positioned while the MT connector C is finely adjusted inthe insertion hole 302. Then, fitting pins are inserted into the holes.In this way, the relative position between the MT connector C and theoptical module 100 in the in-plane direction of the circuit substrate300 is exactly determined. That is, the guide pin holes C1 and the guideholes 53 form a mechanism for positioning in the in-plane direction. Inthis embodiment, the guide pin is inserted from the rear side. However,the position of the optical module 100 and the position of the MTconnector C may be finely adjusted by the MT connector C with a guidepin and the optical module 100 and the MT connector C may be alignedwith each other. In addition, the guide pin hole C1 and the guide hole53 may be visually aligned with each other from the lower side in theinsertion direction of the MT connector C, without using a guide pin.Alternatively, an alignment mark (not illustrated) provided on anoptical connection surface of the optical module may be aligned with analignment mark (not illustrated) provided on the MT connector C.

Then, the latch structure 504 of the cover 500 is fitted to the socket400 to fix the cover 500 to the socket 400. Then, the pressing plate 503is urged by the spring 502 to press the optical module 100 against themounting portion 402. As a result, the height of the optical module 100with respect to the circuit substrate 300 is fixed. The thickness of theoptical module 100 varies in the range of a tolerance. The opticalmodule 100 is pressed by the spring 502 and the pressing plate 503 andis stably pressed by pressing force, regardless of a variation in thethickness of the optical module 100. In particular, the optical module100 is uniformly pressed by the pressing plate 503, which is preferable.In this embodiment, the cover 500 is fixed after positioning in thehorizontal direction. However, the invention is not limited thereto. Thecover 500 may be fixed to the socket before positioning in thehorizontal direction.

In this case, the pin 402 a with a spring which is provided in themounting portion 402 is provided so as to correspond to each planarelectrode pad 16 formed on the substrate mounting surface 12 a of theoptical module 100. The electrical connection between the wiring pattern301 of the circuit substrate 300 and the planar electrode pads 16 of theoptical module 100 is ensured by the pins 402 a with springs.

That is, in the mounting system 2000, it is possible to ensure theelectrical connection between the circuit substrate 300 and the opticalmodule 100, without permanently mounting the optical module 100 to thecircuit substrate 300 using, for example, solder, and to evaluate theoptical module 100. In addition, it is possible to easily remove theoptical module 100 and thus to easily perform maintenance.

The optical module 100 is combined with the optical waveguide which isinstalled in various ways or has various structures in actual use.Therefore, the height of the focusing position of laser light which isemitted from the VCSEL array element 20 through the microlens arrayelement 40 in the optical module 100 is designed depending on theoptical waveguide to be combined with the optical module 100.

In the mounting system 2000, the height-direction positioning mechanismformed by the MT connector supporting member 600 and the spacer 700 candetermine the relative height between the end surface of the opticalfiber provided in the MT connector C and the focusing position of themicrolens array element 40 and accurately align the light receivingsurface of the MT connector C with the focusing position of themicrolens array element 40 in the height direction. In addition, thespacer 700 with a thickness corresponding to the height of the focusingposition of the microlens array element 40 and the MT connectorsupporting member 600 including the supporting pillar 601 with a heightcorresponding to the height of the focusing position of the microlensarray element 40 may be used. In this case, it is possible to accuratelyposition the height of the light receiving surface of the MT connector Cwith respect to the optical module 100 to be combined with the opticalwaveguide which is provided in various ways or has various structures.Therefore, it is possible to apply the optical module 100 to a pluralityof optical modules. When the spacer 700 is made of an elastic material,the relative distance between the circuit substrate and the connectionend surface of the MT connector C can be changed. In this embodiment,the connection end surface of the MT connector C does not come intocontact with the optical module. Therefore, even when unexpected forceis applied to the MT connector, the damage of the optical mode due tothe force is prevented.

The optical module mounting system according to this embodiment issuitably used as an optical module evaluation kit since the opticalmodule is easily removed. In this case, the MT connector C is connectedto an external device, such as a transmission characteristic evaluationdevice for evaluating the transmission characteristics (for example, abit error rate or jitter) of the optical module 100, through amulti-core optical fiber cable.

As a detailed example of the evaluation method, for example, a powersupply voltage, a differential high frequency signal, and a controlsignal are supplied from the wiring pattern 301 of the circuit substrate300 to the optical module 100 through the planar electrode pads 16 tooperate the optical module 100 in a state close to the actual use. TheMT connector C receives the laser optical signal L output from theoptical module 100 and the laser optical signal L is transmitted to thetransmission characteristic evaluation device through the multi-coreoptical fiber cable. Then, transmission characteristics are evaluated ina state close to the actual use.

As described above, according to the mounting system 2000 of the sixthembodiment, it is possible to easily align the optical coupling memberin both the horizontal direction and the vertical direction in a shorttime, using the insertion hole 302. Therefore, manufacturability isimproved. In addition, it is possible to accurately position and fix theoptical module, without mounting the optical module on the circuitsubstrate 300 using, for example, soldering, that is, without the damageof the optical module due to mounting. Therefore, it is easy to removethe optical module from the circuit substrate and maintenance isimproved. Furthermore, when the mounting system 2000 according to thisembodiment is used in an evaluation kit, it is possible to accuratelyevaluate the characteristics of the optical module 100 including highfrequency characteristics.

Seventh Embodiment

FIG. 30 is a cross-sectional view illustrating a portion of a mountingsystem according to a seventh embodiment of the invention. A mountingsystem 2000A according to the seventh embodiment differs from themounting system 2000 according to the sixth embodiment in that awaveguide supporting member 620 replaces the MT connector C and anorganic optical waveguide W, which is a light receiving member (opticalcoupling member) optically coupled to the optical module 100, isprovided on the waveguide supporting member 620. FIG. 31 is a diagramschematically illustrating the waveguide supporting member 620 and theorganic optical waveguide W. In this embodiment, the waveguidesupporting member 620 which is arranged only in the vicinity of theoptical coupling portion is illustrated. However, the waveguidesupporting member 620 may have a longitudinal shape along the lowersurface of the organic optical waveguide W.

One end of the organic optical waveguide W is formed so as to beinclined at an angle of 45 degrees and is processed into a wedge portionW1. The waveguide supporting member 620 and the organic opticalwaveguide W are bonded to each other by, for example, an adhesive. Thewaveguide supporting member 620 has guide holes 620A. The organicoptical waveguide W is connected to a transmission characteristicevaluation device through a multi-core optical fiber cable.

In the mounting system 2000A, the organic optical waveguide W ispositioned in the height direction by the waveguide supporting member620, similarly to the sixth embodiment. In addition, the position of theorganic optical waveguide W in the horizontal direction is finelyadjusted in the MT connector supporting hole 602 such that the guideholes 620A and the guide pin holes provided in the optical module arealigned by guide pins.

As described above, according to the mounting system 2000A of theseventh embodiment, it is possible to easily align an optical couplingmember, using the insertion hole 302. Therefore, manufacturability isimproved. In addition, it is possible to accurately position and fix theoptical module, without mounting the optical module on the circuitsubstrate 300 using, for example, soldering. Therefore, maintenance isimproved. Furthermore, when the mounting system 2000A according to thisembodiment is used in an evaluation kit, it is possible to accuratelyevaluate the characteristics of the optical module 100 including highfrequency characteristics.

In the mounting systems 2000 and 2000A according to the sixth andseventh embodiments, the optical module 100 may be mounted on thecircuit substrate by a method for fixing the cover 500 to the socket 400with, for example, screws, without using a latch structure, to form acircuit substrate which is actually used. In addition, when it is notnecessary to replace the optical module, the optical module may bedirectly fixed to a circuit pattern provided on the circuit substrateby, for example, solder, without using a socket or a cover.

FIG. 32 is a diagram schematically illustrating a circuit substrate onwhich the optical module is mounted using components of the mountingsystem. An optical module-mounted circuit substrate 3000 illustrated inFIG. 32 is formed by mounting the optical module 100 on the circuitsubstrate 200 illustrated in FIG. 7 using the socket 400 and the cover500. The mounting systems according to the sixth and seventh embodimentscan evaluate the optical module in a state close to the actual use.Therefore, the mounting systems can be used when the optical module ismounted on the circuit substrate which is actually used. The opticalmodule-mounted circuit substrate 3000 is suitable for a long-term usesince the optical module 100 can be easily replaced.

In the optical module-mounted circuit substrate 3000 illustrated in FIG.32, an organic optical waveguide 210A having guide holes 211Aillustrated in FIG. 33 may be used instead of the organic opticalwaveguide 210. In the organic optical waveguide 210A, fitting pins areinserted into the guide holes 211A and the guide holes 53 of the opticalmodule 100 to accurately determine the relative position between theorganic optical waveguide 210A and the optical module 100 in the planedirection of the circuit substrate 200.

The springs 502 and 505 provided in the cover 500 are not limited to acoil shape and may be, for example, leaf springs. In addition, it ispreferable that the pressing plate 503 be made of a material with highthermal conductivity such as aluminum. In this case, it is possibledissipate heat generated during the operation of the optical module 100.

In addition, the socket may not include the mounting portion. In thiscase, instead of the pins as the conductive members, solder balls whichhave substantially the same height may be arranged as members forensuring the electrical connection between the planar electrode pads 16of the optical module 100 and the wiring pattern 301 of the circuitsubstrate 300 on the wiring pattern 301. Alternatively, an anisotropicconductive film may be provided between the optical module 100 and thecircuit substrate 300. When the anisotropic conductive film is pressedby the planar electrode pads 16 protruding from the substrate mountingsurface 12 a, only the pressed portion has conductivity. Therefore, anelectrical connection is made only between the planar electrode pad 16and the wiring pattern 301 which face each other. In contrast, noelectrical connection is made between the planar electrode pad 16 andthe wiring pattern 301 which do not face each other, between the planarelectrode pads 16, and between the wiring patterns 301.

In addition, instead of the supporting pillar, a coil spring or a leafspring may be provided in the MT connector supporting member.

In the sixth embodiment, a spacer may be provided between the lens arrayelement holder 50 of the optical module 100 and the MT connector C. Inaddition, other types of optical connectors may be used instead of theMT connector C.

The mounting system according to the above-described embodiment may beused as an optical module for reception. In this case, the MT connectorC or the organic optical waveguide W is connected as a light emittingmember (optical coupling member) which is optically coupled to theoptical module for reception to an array signal light source through amulti-core optical fiber cable. The optical module for receptionreceives an optical signal from the array signal light source andoutputs an electric signal. This system may also be used as anevaluation kit. In this case, the output electric signal is transmittedto the transmission characteristic evaluation device through the wiringpattern of the circuit substrate and the characteristics thereof aremeasured. In this way, it is possible to evaluate the optical module forreception.

In the sixth embodiment, instead of the MT connector C, a lightreceiving module including a photodiode array element and an amplifiermay be directly provided. In this case, it is possible to accuratelyevaluate the characteristics of the optical module 100 itself withoutincluding the characteristics of the MT connector C or the multi-coreoptical fiber cable. When the optical module to be evaluated is anoptical module for reception, a light emitting module including theVCSEL array element and the driver IC may be directly provided, insteadof the MT connector C.

In the circuit substrate, for example, a ridge optical waveguide, suchas a silicon wire waveguide, an optical fiber sheet, or a PLC chip maybe used instead of the organic optical waveguide to be opticallycoupled.

Eighth and Ninth Embodiments

FIG. 34 is a diagram schematically illustrating an opticalmodule-mounted circuit substrate according to an eighth embodiment. FIG.35 is a diagram schematically illustrating an optical module-mountedcircuit substrate according to a ninth embodiment.

Optical module-mounted circuit substrates 4000 and 5000 each include anoptical module 100, a circuit substrate 200, and an organic opticalwaveguide 210. The optical module-mounted circuit substrates 4000 and5000 according to the eighth and ninth embodiments differ from theoptical module-mounted circuit substrates according to the sixth andseventh embodiments in that, while the optical module is mounted on thecircuit substrate through the socket in the sixth and seventhembodiments, the optical module 100 is directly fixed to a wiringpattern 201 on the circuit substrate 200 by, for example, solder and iselectrically connected thereto and the organic optical waveguide 210,which is an optical coupling member, is directly fixed to the circuitsubstrate 200 by, for example, an adhesive (through a spacer ifnecessary) in the eighth and ninth embodiments. The eighth embodimentdiffers from the ninth embodiment in that the organic optical waveguide210, which is an optical coupling member, is fixed between the opticalmodule and the circuit substrate on the circuit substrate or the organicoptical waveguide 210 is provided on the lower surface of the circuitsubstrate such that the circuit substrate is interposed between theoptical module and the organic optical waveguide. According to thesemethods, after the optical module 100 is fixed, an alignment mark (notillustrated) provided on the organic optical waveguide 210 and analignment mark (not illustrated) provided on the optical module arevisually aligned with each other through an opening 202, which has thesame shape as the insertion hole 302 of the circuit substrate 300, inthe horizontal direction on the plane of the circuit substrate 200.Therefore, it is possible to easily determine an optical couplingposition and manufacturability is improved. In the method using theguide pin hole as the alignment mark, the outside diameter of theorganic optical waveguide can also be aligned with the mark provided onthe optical module. In the eighth and ninth embodiments, the opticalmodule may be detachably and electrically fixed using the socket,instead of using soldering.

As illustrated in FIGS. 34 and 35, the opening 202 may be a through holeprovided in the circuit substrate 200 or an optical window in which ahole is filled with, for example, an optical glass 203. In addition, theopening 202 may be an optical via or a spot size conversion mechanismhaving a lens provided therein.

In this embodiment, the optical coupling member is not limited to theorganic optical waveguide 210. For example, the organic opticalwaveguide 210 may be a planar waveguide, such as a PLC, or a 90-degreebent optical connector having a connection end surface on the opticalmodule side.

In the sixth to ninth embodiments, after positioning in the horizontaldirection is performed, it is possible to perform active alignment whileseeing an output from an optical detector which is provided at the otherend of the organic waveguide. Therefore, it is possible to accuratelyperform alignment.

It is most preferable that the opening 302 or 202 be provided in thevicinity of an optical coupling portion. When the position of theoptical module and the position of the optical coupling member arealigned with each other through the opening, the opening 302 or 202 maybe provided at a position other than the vicinity of the opticalcoupling portion.

Tenth Embodiment

FIG. 36 is a perspective view schematically illustrating an opticalmodule according to a tenth embodiment of the invention. An opticalmodule 100E according to the tenth embodiment differs from the opticalmodule 100 according to the first embodiment illustrated in FIG. 1 inthat a lens array element holder 50E replaces the lens array elementholder 50.

The lens array element holder 50E holds a microlens array element 40. Inaddition, the lens array element holder 50E has guide holes 53E foralignment.

The lens array element holder 50E includes a slit 56E as an attachmentstructure for attaching a protector which protects the microlens arrayelement 40.

FIG. 37 is a side view schematically illustrating a protector. Aprotector 80 has a plate shape as a whole and includes a main body 80 a,a dustproof portion 80 b which is formed at one end of the main body 80a and is thicker than the main body 80 a, a through hole 80 c which isformed in the dustproof portion 80 b, and an insertion portion 80 dwhich is formed at the other end of the main body 80 a opposite to thedustproof portion 80 b and is thinner than the main body 80 a.

FIG. 38 is a diagram illustrating a state in which the protector isattached to the optical module. When the protector 80 is attached to theoptical module 100E, the insertion portion 80 d of the protector 80 isinserted into the slit 56E of the lens array element holder 50E. In thisway, the protector 80 is attached to the lens array element holder 50E,without interfering with the microlens array element 40.

In the optical module 100E, a surface of the microlens array element 40on which microlens are formed is exposed. However, since the protector80 is attached, the surface of the microlens array element 40 is coveredand protected by the main body 80 a. In addition, when the insertionportion 80 d is inserted into the slit 56E, the dustproof portion 80 bcomes into contact with the front side wall of the lens array elementholder 50E and prevents, for example, dust from reaching the microlensarray element 40 from the outside.

The protector 80 is attached to the optical module 100E when the opticalmodule 100E is in storage or while the optical module 100E is beingtransported with being accommodated in a reel tape. In some cases, dustis generated in the vicinity of the optical module 100E during thestorage or transportation of the optical module 100E. When dust isattached to the surface of the microlens array element 40 on which themicrolens are formed, the optical characteristics of the optical module100E deteriorate due to the dust.

In contrast, the structure in which the protector 80 is attached to theoptical module 100E can prevent, for example, dust from being attachedto the surface of the microlens array element 40 on which the microlensare formed even when dust is generated in the vicinity of the opticalmodule 100E during the storage or transportation of the optical module100E. The optical module 100E is accommodated in a case while beingtransported. For example, dust is generated when the friction betweenthe optical module 100E and the case occurs due to vibration. Theprotector 80 is effective in protecting the optical module 100E from,for example, dust.

The protector 80 may be attached to the optical module 100E during asolder reflow mounting process. During the solder reflow mountingprocess, dust or a scatter (for example, flux) from solder cream (paste)floats in a reflow furnace. The protector 80 is effective in protectingthe optical module 100E from, for example, the floating matter.

For example, when the optical module 100E is mounted to the circuitsubstrate 200 illustrated in FIG. 7 by solder reflow, first, theprotector 80 is attached to the optical module 100E. Then, the solderreflow mounting process is performed in the reflow furnace to mount theoptical module 100E to the circuit substrate 200. Then, the circuitsubstrate 200 is taken out from the reflow furnace and the protector 80is removed from the optical module 100E. When the protector 80 isremoved, it is possible to ensure an optical path between the microlensarray element 40 and an organic optical waveguide 210 mounted on thecircuit substrate 200. In addition, for example, the user can insert afinger or a hook into the through hole 80 c and draw the protector 80 toeasily remove the protector 80 from the optical module 100E.

As described above, when the protector 80 is used in the solder reflowmounting process, the protector 80 is made of a material with asufficient heat resistance to withstand the internal temperature of thereflow furnace. In addition, it is preferable that the protector 80 bemade of a material with sufficient elasticity to press the insertionportion 80 d into the slit 56E by press fitting. In this case, it ispossible to easily fix the protector 80 to the lens array element holder50E. Therefore, the material forming the protector 80 is preferablyTeflon (registered trademark) which has high heat resistance and iscapable of pressing the insertion portion 80 d into the slit 56E.

FIGS. 39 and 40 are diagrams schematically illustrating protectorsaccording to other embodiments. FIG. 39 is a cross-sectional viewillustrating the optical module 100E having a protector 80A attachedthereto (corresponding to the cross-sectional view of FIG. 4) and FIG.40 is a front view. In FIG. 40, the protector 80A is represented by adashed line. The protector 80A includes a protective portion 80Aa whichhas a plate shape, covers the surface of the microlens array element 40,and has one end inserted into the slit 56E of the lens array elementholder 50E and a spring portion 80Ab which forms a U-shape together withthe protective portion 80Aa as viewed from a side surface and is used tofix the protector 80A to the optical module 100E.

The protective portion 80Aa covers and protects the surface of themicrolens array element 40, with one end of the protective portion 80Aaof the protector 80A being inserted into the slit 56E, and the protector80A is fixed to the optical module 100E while the optical module 100E isinterposed between the protective portion 80Aa and the spring portion80Ab.

FIGS. 41A and 41B are diagrams illustrating an aspect in which theoptical module 100E having the protector 80A attached thereto is mountedto the circuit substrate 200. However, the protector 80A is notillustrated in FIG. 41B for convenience of explanation. When the opticalmodule 100E is mounted on the circuit substrate 200, the optical module100E is mounted on the circuit substrate 200 onto which solder has beenapplied. The same mounter as that used to mount an electronic componentis used to mount the optical module 100E. In addition, pins 211B areformed on the circuit substrate 200 and an optical waveguide 210B havinga waveguide core 212B is mounted on the circuit substrate 200. When theoptical module 100E is mounted, for example, an image recognitionprocess is performed for the guide holes 17 (see FIG. 36) of the opticalmodule 100E and the pins 211B of the circuit substrate 200 and analignment process is performed by the mounter. Then, the optical module100E is mounted on the circuit substrate 200. In addition, holes may beformed instead of the pins 211B. Then, the circuit substrate 200 havingthe optical module 100E mounted thereon is guided into the reflowfurnace and the solder reflow mounting process is performed for thecircuit substrate 200.

Alternatively, an optical waveguide 210 having the pins 211B formedthereon is mounted. When the optical module 100E is mounted, an imagerecognition process is performed for the guide holes 53E (see FIG. 36)for alignment which are provided in the lens array element holder 50E ofthe optical module 100E and two pins 211B (see FIG. 41B) of the circuitsubstrate 200 and an alignment process is performed by the mounter.Then, the optical module 100E is mounted on the circuit substrate 200.Then, the circuit substrate 200 having the optical module 100E mountedthereon is guided into the reflow furnace and the solder reflow mountingprocess is performed for the circuit substrate 200.

The guide holes 53E of the optical module 100E and the pins 211B of thecircuit substrate 200 are designed in advance so as to be fitted to eachother when the alignment process is performed by the mounter and theoptical module 100E is mounted on the circuit substrate 200. The opticalmodule 100E is designed in advance such that a known MT ferrule attachedto an optical fiber tape is aligned with the guide hole 53E through theguide pin and the optical module 100E is evaluated. That is, the opticalmodule 100E is aligned and assembled such that the positionalrelationship among the optical fiber core of the MT connector, themicrolens array element 40, and the VCSEL array element 20 falls withina desired optical loss range (optical coupling loss range). Thepositional relationship between the pin 211B and the waveguide core 212Bis designed in advance such that light emitted from the microlens arrayelement 40 of the optical module 100E is optically coupled to apredetermined waveguide core 212B of the optical waveguide 210B in adesired optical loss range (optical coupling loss range) when theoptical module 100E is mounted on the circuit substrate 200. Then, theoptical module 100E and the circuit substrate 200 are manufactured onthe basis of the design.

According to the above-mentioned structure, the fitting between the(two) guide holes 53E and the (two) pins 211B makes it possible to solvethe problem that the positional deviation between the optical module100E and the optical waveguide 210B occurs due to, for example,vibration during a process for a period from the mounting of the opticalmodule 100E by the mounter to the end of the solder reflow mountingprocess, which causes the damage of the favorable optical couplingbetween the optical module 100E and the optical waveguide 210B. Inaddition, the fitting makes it possible to reliably perform the opticalcoupling between the optical module 100E and the optical waveguide 210Bformed on the circuit substrate 200.

It is assumed that the clearance (which is substantially equal to thedifference between the inside diameter of the guide hole 53E and theoutside diameter of the pin 211B) between the guide hole 53E of the lensarray element holder 50E and the pin 211B is c1 and the clearance (whichis substantially equal to the difference between the internal width ofthe frame member 12 and the width of the optical waveguide 210B in theleft-right direction of the plane of paper in FIG. 41B) between theframe member 12 of the optical module 100E and the optical waveguide210B is c2. In this case, the components are designed so as to satisfyc1<c2. According to this structure, the clearance c2 has the effect ofguiding the fitting between the guide hole 53E and the pin 211B and thefitting is reliably performed.

It is preferable to use the following structure in order to reliablyperform the above-mentioned alignment and to easily perform mountingwhen the alignment process is performed by the mounter and the opticalmodule 100E is mounted on the circuit substrate 200 by the fittingbetween the guide holes 53E provided in the optical module 100E and thepins 211B provided on the optical waveguide 210B. FIG. 59A is aperspective view schematically illustrating an optical module accordingto a modification of the tenth embodiment. FIG. 59B is a diagramillustrating a state in which the protector is attached to the opticalmodule. FIG. 59C is a top view illustrating a main portion illustratedin FIG. 59B. FIG. 59D is a cross-sectional view illustrating a mainportion taken along the line D-D of FIG. 59C. FIG. 59E is a diagram asviewed from an arrow E in FIG. 59C. An optical module 100E1 according tothis modification differs from the optical module 100E according to thetenth embodiment in that a lens array element holder 50E1 replaces thelens array element holder 50E. The lens array element holder 50E1differs from the lens array element holder 50E in that a groove-shapeddepressed portion 57E1 is formed in the lens array element holder 50E1.One of the guide holes 53E is formed in the bottom of the depressedportion 57E1.

The depth of the depressed portion 57E1 is greater than the length ofthe pin 211B provided on the optical waveguide 210B and is less than thelength of the guide pin used to fit the MT ferrule.

That is, when the optical module 100E is mounted on the circuitsubstrate 200, one of the two pins 211B provided on the opticalwaveguide 210B is fitted to the guide hole 53E and the other pint isfitted to the depressed portion 57E1. For example, when the guide pin isinserted into the guide hole 53E and the guide pin and a known MTferrule are fitted so as to be optically connected to each other inorder to evaluate only the optical module 100E1, one of the two guidepins is fitted to the guide hole 53E in which the depressed portion 57E1is not formed and the other guide pin is fitted to the guide hole 53Eprovided in the bottom of the depressed portion 57E1.

The following effect is obtained by the formation of the depressedportion 57E1. In a case in which the alignment process is performed bythe mounter and the optical module 100E1 is mounted on the circuitsubstrate 200, even when the clearance between the guide hole 53E andthe pin 211B is reduced in order to improve the accuracy of fitting oreven when there is a little deviation in the gap between the two pins211B, it is possible to easily fit the pins 211B to the guide holes 53Eand the depressed portion 57E1 since the depressed portion 57E1 is along hole. As a result, it is possible to prevent the problem that it isdifficult to fit the optical waveguide 210B to the optical module 100E.

That is, since one of the guide holes 53E is formed in the bottom of thedepressed portion 57E1, the optical module 100E1 and a known MT ferruleare fitted so as to be optically connected to each other and the opticalmodule 100E1 can be easily evaluated. In addition, when the opticalmodule 100E is mounted on the circuit substrate 200, it is possible toeasily fit the optical waveguide 210B to the optical module 100E.

The edge of the guide hole 53E (that is, the edge of the depressedportion 57E1) into which the pin 211B is inserted may be a taperedportion 57E1 a (see FIGS. 59D and 59E) which is slightly chamfered, inorder to reliably prevent non-fitting and to reliably fit the pin 211Bto the guide hole 53E.

The pin is formed in a tapered shape, for example, a truncated coneshape by, for example, photolithography like a pin 211B1 formed on anoptical waveguide 210B1 illustrated in FIG. 60. According to thisstructure, it is possible to improve ease of fitting during mounting andto improve the accuracy of the positioning between the optical module100E and the optical waveguide 210B1.

FIGS. 42 and 43 are diagrams schematically illustrating a protectoraccording to another embodiment. FIG. 42 is a side cross-sectional view(corresponding to the cross-sectional view of FIG. 4) illustrating theoptical module 100E having a protector 80B attached thereto and FIG. 43is a front view. In FIG. 43, the protector 80B is represented by adashed line. The protector 80B includes a protective portion 80Ba whichhas a plate shape, covers the surface of the microlens array element 40,and has one end inserted into the slit 56E of the lens array elementholder 50E, a spring portion 80Bb which forms a U-shape together withthe protective portion 80Ba as viewed from a side surface and is used tofix the protector 80B to the optical module 100E, and a bent portion80Bc which is provided between the protective portion 80Ba and thespring portion 80Bb.

The protective portion 80Ba covers and protects the surface of themicrolens array element 40, with one end of the protective portion 80Baof the protector 80B being inserted into the slit 56E, and the protector80B is fixed to the optical module 100E while the optical module 100E isinterposed between the protective portion 80Ba and the spring portion80Bb. In addition, the gap between the protector 80B and the lens arrayelement holder 50E of the optical module 100E is reduced by the bentportion 80Bc. Therefore, it is possible to prevent, for example, dustfrom getting into the optical module 100E from the outside.

The protector 80A or 80B may be a plastic molding or may be a leafspring manufactured by bending one metal plate. In the protectors 80Aand 80B, the spring force of the spring portion 80Ab or 80Bb canreliably reduce the risk of the detachment of the protector 80A or 80Bfrom the optical module 100E and it is possible to improve thereliability of a protection function.

In the solder reflow mounting process, the internal temperature of thereflow furnace is high. Therefore, when a closed space is present in theoptical module, there is a concern that the internal pressure of theclosed space will increase.

However, in the optical module according to the above-describedembodiment, for example, in the optical module 100, the inner portionwhich is covered with the lens array element holder 50 is connected toan external space through the guide hole 53 or the gap between themicrolens array element 40 and the holding hole 52 for fixing themicrolens array element 40. Therefore, even in the solder reflowmounting process, an increase in the internal pressure of the opticalmodule or damage due to pressure is prevented.

As described above, after the solder reflow mounting process, a processof filling the gap of the mounting surface with an underfill material isperformed. In this process, it is preferable to use the following heightadjuster.

FIG. 44 is a top view schematically illustrating the height adjuster.FIG. 45 is a side view schematically illustrating the height adjuster.As illustrated in FIGS. 44 and 45, a height adjuster 80C has a plateshape as a whole and includes a main body 80Ca, a height adjustmentportion 80Cb which is formed at one end of the main body 80Ca, isthicker than the main body 80Ca, and is wider than the main body 80Ca, athrough hole 80Cc for an optical path which is formed in the main body80Ca, and an insertion portion 80Cd which is provided at the other endof the main body 80Ca opposite to the height adjustment portion 80Cb andis thinner than the main body 80Ca.

Next, the usage and effect of the height adjuster 80C will be described.First, a case in which the gap of the mounting surface is filled withthe underfill material, without using the height adjuster 80C, will bedescribed.

FIG. 46 is a diagram illustrating a case in which the height adjuster isnot used. Here, an example in which the circuit substrate 1000 (see FIG.8) formed by mounting the optical module 100 on the circuit substrate200 is filled with the underfill material will be described.

The gap between the optical module 100 and the circuit substrate 200 isfilled with an underfill material UF. However, since the optical module100 has the waveguide introduction opening 15, the height of the gap tobe filled with the underfill material UF on the side of the waveguideintroduction opening 15 is from the surface of the circuit substrate 200to the surface of the lens array element holder 50E and is greater thanthe height from the surface of the circuit substrate 200 to thesubstrate mounting surface 12 a. As such, when the large gap is filledwith the underfill material UF, the amount of underfill material UF usedincreases. In addition, a material with high viscosity needs to be usedas the underfill material UF. As a result, flexibility in the selectionof the material to be used as the underfill material UF is reduced.

In contrast, FIG. 47 is a diagram illustrating a case in which theheight adjuster is used. FIG. 47 illustrates a circuit substrate 1000Eformed by mounting the optical module 100E on the circuit substrate 200.

As described above, in the case in which the protector is attached tothe optical module 100E and the solder reflow mounting process isperformed, the protector is removed after the optical module 100E ismounted. Then, the height adjuster 80C is attached to the optical module100E. Specifically, the insertion portion 80Cd of the height adjuster80C is inserted into the slit 56E of the lens array element holder 50E.In this way, the height adjuster 80C is attached to the lens arrayelement holder 50E. In the inserted state, the through hole 80Cc for anoptical path is located at a corresponding position on the surface ofthe microlens array element 40 on which the microlenses are formed. Theoptical path between the microlens array element 40 and the organicoptical waveguide 210 is ensured by the through hole 80Cc for an opticalpath.

In the inserted state, the thickness of the height adjustment portion80Cb is adjusted such that the lower end of the height adjustmentportion 80Cb of the height adjuster 80C is substantially flush with orlower than the substrate mounting surface 12 a of the optical module100E. Therefore, when the gap between the optical module 100E and thecircuit substrate 200 is filled with the underfill material UF, it maybe filled up to a height corresponding to the lower end of the heightadjustment portion 80Cb on the side of the waveguide introductionopening 15. In this case, an increase in the amount of underfillmaterial UF used is prevented and flexibility in the selection of thematerial to be used as the underfill material UF increases. In addition,since the optical path between the microlens array element 40 and theorganic optical waveguide 210 is ensured by the through hole 80Cc for anoptical path, it is possible to use the circuit substrate 1000E, withthe height adjuster 80C attached to the circuit substrate 1000E. It ispreferable that the width of the height adjustment portion 80Cb besubstantially equal to the width of the waveguide introduction opening15.

The application of the protector is not limited to the optical moduleaccording to the above-described embodiment, but the protector may beapplied to the optical modules according to other embodiments.

FIG. 48 is a perspective view schematically illustrating an opticalmodule according to another embodiment to which the protector will beapplied. An optical module 900 includes a circuit substrate 950, ahousing 910 which covers the circuit substrate 950, a light input/outputportion 914 which is formed on the circuit substrate 950, and two guidepins 918 which are formed on the light input/output portion 914. Twoguide portions 910 a for guiding an MT connector C2, which will bedescribed below, to the light input/output portion 914 are formed at theleading end of the housing 910. Each guide portion 910 a has two grooves910 ab formed in a side surface thereof. A driver IC which is anelectronic element is mounted on the circuit substrate 950 in thehousing 910, similarly to, for example, the optical module 100.

FIG. 49 is a cross-sectional view taken along the line C-C of FIG. 48.The VCSEL array element 20 is mounted below the light input/outputportion 914 on the circuit substrate 950. The VCSEL array element 20 iselectrically connected to the driver IC by a bonding wire 901. The lightinput/output portion 914 has opening portions 914 a, 914 b, and 914 cwhich are formed in the upper and lower surfaces and a side surface (thesurface on which the guide pin 918 is formed). The light input/outputportion 914 accommodates a prism lens array 915. The prism lens array915 is arranged so as to correspond to the VCSEL array element 20. Inthe prism lens array 915, for example, 12 microlenses 915 acorresponding to the number of VCSEL elements in the VCSEL array element20 are arranged in a one-dimensional array on a side surface (thesurface in which the opening portion 914 b is formed) of a prism. Theprism lens array 915 reflects a laser optical signal output from eachVCSEL element and focuses the laser optical signal to achievepredetermined optical coupling to an external optical component, asrepresented by, for example, an optical path P. The prism lens array 915is exposed to the outside through the opening portions 914 a and 914 b.

Returning to FIG. 48, the MT connector C2 is connected to the lightinput/output portion 914 of the optical module 900. The MT connector C2has a structure in which a ferrule 960 is attached to the leading end ofan optical fiber tape 970. The ferrule 960 has two guide holes 966 intowhich the two guide pins 918 of the light input/output portion 914 areinserted. When the MT connector C2 is connected to the lightinput/output portion 914, the ferrule 960 of the MT connector C2 isinserted between the two guide portions 910 a and the two guide pins 918are inserted into the two guide holes 966 to connect the lightinput/output portion 914 to the MT connector C2. Then, the MT connectorC2 is fixed to the optical module 900 using the grooves 910 ab of theguide portions 910 a and a predetermined fixing tool.

Next, a protector which can be applied to the optical module illustratedin FIG. 48 will be described. FIG. 50 is a perspective viewschematically illustrating the protector which can be applied to theoptical module illustrated in FIG. 48. A protector 90 includes a frontprotective portion 90 a having a flat plate shape, an upper protectiveportion 90 b which is a cover with a rectangular parallelepiped shape,extends from the front protective portion 90 a in a directionperpendicular to the main surface of the front protective portion 90 a,and has openings formed in a lower surface and a surface opposite to thefront protective portion 90 a, two fixing arms 90 c which extend fromthe front protective portion 90 a along both side surfaces of the upperprotective portion 90 b, a lower protective portion 90 d which extendsfrom the front protective portion 90 a along an opening formed in thelower surface of the upper protective portion 90 b, and a substratefitting portion 90 e which extends from the lower protective portion 90d and forms a step portion together with the lower protective portion 90d. The fixing arm 90 c has a fitting portion 90 ca which protrudestoward the lower protective portion 90 d. The fixing arm 90 c issubstantially parallel to the lower protective portion 90 d. Forexample, the protector 90 is manufactured by bending one metal plate.

FIGS. 51 and 52 are diagrams illustrating a state in which the protectorillustrated in FIG. 50 is attached to the optical module illustrated inFIG. 48. When the protector 90 is attached to the optical module 900,first, the light input/output portion 914 is covered with the upperprotective portion 90 b from the leading end of the optical module 900and the protector 90 is slid to the optical module 900. Then, thesubstrate fitting portion 90 e is inserted between the two guideportions 910 a and each guide portion 910 a is interposed between eachfixing arm 90 c and the lower protective portion 90 d by the springforce of each fixing arm 90 c. In this case, the fitting portion 90 caformed in the fixing arm 90 c is fitted to the groove 910 ab formed inthe guide portion 910 a. The protector 90 is fixed to the optical module900 by the fitting.

In the state in which the protector 90 is attached to the optical module900, a portion of the prism lens array 915 which is exposed through theopening portion 914 a is covered and protected by the upper protectiveportion 90 b. In addition, a portion of the prism lens array 915 whichis exposed through the opening portion 914 b is covered and protected bythe front protective portion 90 a. The lower protective portion 90 dprevents, for example, dust from getting into the optical module fromthe lower side between the guide portions 910 a. In this case, since thesubstrate fitting portion 90 e is inserted between the guide portion 910a, the formation of a gap between the circuit substrate 950 and thelower protective portion 90 d is prevented.

The protector 90 is attached to the optical module 900 when the opticalmodule 900 is in storage or while the optical module 900 is beingtransported with being accommodated in a reel tape. In some cases, dustis generated in the vicinity of the optical module 900 during thestorage or transportation of the optical module 900. When dust isattached to the surface of the prism lens array 915, the opticalcharacteristics of the optical module 900 deteriorate due to the dust.

In contrast, the structure in which the protector 90 is attached to theoptical module 900 can prevent, for example, dust from being attached tothe surface of the prism lens array 915 even when dust is generated inthe vicinity of the optical module 900 during the storage ortransportation of the optical module 900.

When the optical module 900 is mounted on the circuit substrate, theprotector 90 may be attached to the optical module 900 during the solderreflow mounting process. During the solder reflow mounting process, dustor a scatter from solder cream floats in the reflow furnace. Theprotector 90 is effective in protecting the optical module 900 from, forexample, the floating matter.

After the optical module 900 is mounted on the circuit substrate, theprotector 90 is removed. Then, the MT connector C2 is connected asillustrated in FIG. 48.

FIG. 53 is a perspective view schematically illustrating a protectoraccording to another embodiment. FIG. 54 is a diagram illustrating astate in which the protector illustrated in FIG. 53 is attached to theoptical module illustrated in FIG. 48. A protector 90A illustrated inFIGS. 53 and 54 differs from the protector 90 illustrated in FIG. 50 inthe shape of a fixing arm. That is, while the fitting portion 90 ca ofthe fixing arm 90 c of the protector 90 is fitted to the rear groove ofthe two grooves 910 ab formed in the guide portion 910 a, a fittingportion 90Aca of a fixing arm 90Ac of the protector 90A is fitted to thefront groove of the two grooves 910 ab formed in the guide portion 910a. The leading end of a protruding portion of the fitting portion 90Acamay be closer to the front protective portion 90 a than the substratefitting portion 90 e. In this case, the clamping force of each fixingarm 90Ac and the lower protective portion 90 d on each guide portion 910a interposed therebetween is increased by the spring force of eachfixing arm 90Ac. As a result, the risk of the protector 90A beingdetached from the optical module 900 is further reduced and a gapbetween the protector 90A and the optical module 900 is less likely tooccur. Therefore, the effect of the protector 90A preventing theentrance of, for example, dust is further improved.

The protector 90A illustrated in FIGS. 53 and 54 includes plate-shapedguide portions 90Af which are provided at positions facing the fixingarms 90 c so as to extend from the lower protective portion 90 d. Theguide portion 90Af extends from the lower protective portion 90 d so asto be inclined downward. The guide portion 90Af makes it easy for theguide portion 910 a of the optical module 900 to be inserted between thefixing arm 90 c and the lower protective portion 90 d.

FIG. 61 is a perspective view schematically illustrating a protectoraccording to another embodiment. FIG. 62 is a side view schematicallyillustrating the protector illustrated in FIG. 61. FIG. 63 is a diagramillustrating a state in which the protector illustrated in FIG. 61 isattached to the optical module illustrated in FIG. 48. FIG. 64 is adiagram illustrating a state in which the protector illustrated in FIG.61 is attached to the optical module illustrated in FIG. 48.

Next, the difference between the protector 90 and a protector 90B willbe mainly described. In the protector 90B, a front protective portion90Ba includes a front protective portion upper part 90Baa and a frontprotective portion lower part 90Bab. The main surface of the frontprotective portion upper part 90Baa extends in a direction perpendicularto an upper protective portion 90 b. The front protective portion lowerpart 90Bab is inclined with respect to the front protective portionupper part 90Baa in the direction in which the upper protective portion90 b extends.

In the protector 90B, two fixing arms 90Bc extend from the frontprotective portion lower part 90Bab along both side surfaces of an upperprotective portion 90 b so as to be inclined with respect to the upperprotective portion 90 b. The fixing arm 90Bc includes a fitting portion90Bca which protrudes toward a lower protective portion 90Bd. The lowerprotective portion 90Bd extends from the front protective portion lowerpart 90Bab along an opening provided in the lower surface of the upperprotective portion 90 b so as to be inclined with respect to the upperprotective portion 90 b. A substrate fitting portion 90Be extends fromthe lower protective portion 90Bd so as to form a step portion togetherwith the lower protective portion 90Bd. A guide portion 90Bf extendsfrom the lower protective portion 90Bd at a position facing the fixingarm 90Bc. As illustrated in FIG. 62, the fixing arm 90Bc and the lowerprotective portion 90Bd are both inclined with respect to alower-surface-side opening 90 bd of the upper protective portion 90 b.The fixing arm 90Bc is substantially parallel to the lower protectiveportion 90Bd.

When the protector 90B is attached to the optical module 900, first, thelight input/output portion 914 is covered with the upper protectiveportion 90 b from the leading end of the optical module 900 and theprotector 90B is slid to the optical module 900. Then, the substratefitting portion 90Be is inserted between two guide portions 910 a andeach guide portion 910 a is interposed between each fixing arm 90Bc andthe lower protective portion 90Bd by the spring force of each fixing arm90Bc. In this case, the fitting portion 90Bca formed in the fixing arm90Bc is fitted to the groove 910 ab formed in the guide portion 910 a.The protector 90B is fixed to the optical module 900 by the fitting. Inaddition, the guide portion 90Bf makes it easy for the guide portion 910a to be inserted between the fixing arm 90Bc and the lower protectiveportion 90Bd.

In the protector 90B, the fixing arm 90Bc and the lower protectiveportion 90Bd are both inclined with respect to the upper protectiveportion 90 b. Therefore, the optical module 900 can be interposedbetween the upper protective portion 90 b and the lower protectiveportion 90Bd. Then, the fixing arm 90Bc is fitted to the guide portion910 a and the guide portion 910 a is interposed between the fixing arm90Bc and the lower protective portion 90Bd. Therefore, even when theoptical module 900 is inclined, the protector 90B does not come off theoptical module 900.

However, in the case of the optical module 900 having theabove-mentioned structure, in the actual use, the opening portionprovided at the upper part of the light input/output portion is opened.Therefore, the upper opening portion may be protected by the followingprotective structure.

FIG. 55 is a diagram illustrating an optical module to which aprotective structure is applied (see Japanese Patent No. 5117640). Anoptical module 800 includes a circuit substrate 850, a housing 810 whichis mounted on the circuit substrate 850, an optical fiber tape 870 whichtransmits an optical signal through a ferrule 860, and a fixing member840 which fixes the ferrule 860 to the housing 810 so as to bedetachable from the housing 810.

A laser module including a light emitting element, such as asemiconductor laser, or a light receiving element, such as a photodiode,may be mounted on the circuit substrate 850. The semiconductor laser maybe a surface-emitting semiconductor laser. The photodiode may be a pinphotodiode. The thickness of the circuit substrate is, for example,about 1.5 mm.

The housing 810 may be made of ceramic. The thickest portion of thehousing 810 may have a thickness of about a few millimeters. Thethickness of the ferrule 860 is equal to or less than 1.6 mm. The fixingmember 840 includes a first pressing portion 830 and a second pressingportion 820, which will be described below. The fixing member 840 isformed by processing a metal plate member with a thickness of about 0.2mm. The metal material forming the fixing member 840 may be, forexample, an aluminum alloy, a copper alloy, or stainless steel.

In the optical module 800, the circuit substrate 850 is coupled to theoptical fiber tape 870 through the ferrule 860. That is, the opticalmodule 800 converts an electric signal from the circuit substrate 850into light and couples the light to the optical fiber tape 870 throughthe ferrule 860. In addition, the optical module 800 converts an opticalsignal from the optical fiber tape 870 into an electric signal andsupplies the electric signal to an element on the circuit substrate 850.In this way, a detachable optical-electric connection is made betweenthe circuit substrate 850 and the optical fiber tape 870.

FIG. 56 is an exploded view illustrating the optical module 800. Theferrule 860 has a light input/output surface 862 to and from which anoptical signal transmitted through a core portion of the optical fibertape 870 is input and output. In FIG. 56, it is assumed that the normaldirection of the light input/output surface 862 is the Y-axis. Inaddition, it is assumed that the normal direction of a mounting surface813, which will be described below, is the Z-axis. It is assumed that adirection perpendicular to both the Y-axis and the Z-axis is the X-axis.At least two guide holes 866 are provided in the light input/outputsurface 862 of the ferrule 860. The guide holes 866 are fitted to guidepins formed on a light input/output portion 814, which will be describedbelow, to position the ferrule 860. The ferrule 860 has a side surface864 having the X-axis as the normal direction.

The housing 810 has a mounting portion 812 on which the ferrule 860 isplaced. The mounting portion 812 may be a thin plate-shape member havinga substantially parallelepiped shape which is provided at an end of thehousing 810 close to the optical fiber tape 870. The mounting portion812 may be provided such that the rear surface of the mounting portion812 is in the same plane as the rear surface of the housing 810. Inaddition, the thickness of the mounting portion 812 in the Z-axisdirection is less than that of a region of the housing 810 in which thelight input/output portion 814, which will be described below, isprovided. The mounting portion 812 may have substantially the same widthas the housing 810 in the X-axis direction.

The mounting portion 812 has the mounting surface 813 which supports theferrule 860. The mounting surface 813 has the Y-axis as a normaldirection. The housing 810 includes the light input/output portion 814which faces the light input/output surface 862 of the ferrule 860. Thelight input/output portion 814 is fixed to the housing 810. The lightinput/output portion 814 receives an optical signal between the lightinput/output surface 862 of the ferrule 860 and the circuit substrate850. An optical element, such as a prism lens array, is accommodated inthe light input/output portion 814. In addition, an opening portion 814a is formed in the upper surface of the light input/output portion 814and a portion of the surface of the optical element accommodated in thelight input/output portion 814 is exposed to the outside through theopening portion 814 a.

The housing 810 includes guide portions 880 which guide the side surface864 of the ferrule 860 in the Y-axis direction. The guide portion 880may be a block-shaped member which extends from a surface of the housing810 facing the ferrule 860 to the optical fiber tape 870. The guideportions 880 are provided at both ends of the mounting portion 812 inthe X-axis direction so as to face each other. Each guide portion 880has a guide surface 882 which is vertical to the mounting surface 813and is parallel to the Y-axis direction. When the ferrule 860 is placedon the mounting portion 812, the guide surface 882 comes into contactwith the side surface 864 of the ferrule 860.

The guide portion 880 includes a first groove 884 and a second groove886 which extend from the front surface to the rear surface of the guideportion 880 in the Z-axis direction. The front surface of the guideportion 880 indicates a surface of the guide portion 880 opposite to themounting portion 812. The rear surface of the guide portion 880indicates a surface of the guide portion 880 which comes into contactwith the mounting portion 812. The first groove 884 and the secondgroove 886 may be through holes which are formed at the outer end of theguide portion 880 and have a U-shape in a cross-sectional view. Theouter end means an end of the guide portion 880 which is opposite to thesurfaces of the two guide portions 880 facing each other.

The first groove 884 and the second groove 886 are arranged in a line inthe Y-axis direction. A distance between the first groove 884 and thesecond groove 886 may be substantially equal to a distance between asupporting portion 832 and a contact portion 822, which will bedescribed below, in the Y-axis direction. The term “substantially equal”means that, when a fixing member 840 is mounted from the upper side ofthe guide portion 880, the distance between the supporting portion 832and the contact portion 822 is equal to the distance between the firstand second grooves such that the supporting portion 832 and the contactportion 822 can pass through the first groove 884 and the second groove886.

The first groove 884 is formed so as to further pass through themounting portion 812. That is, the first groove 884 is formed so as topass through both the guide portion 880 and the mounting portion 812.The second groove 886 may be formed in a region of the guide portion 880which is placed on the circuit substrate 850. The second groove 886 doesnot pass through the circuit substrate 850. In addition, the secondgroove 886 may be formed so as to extend from the front surface of theguide portion 880 to the middle of the guide portion 880. That is, thesecond groove 886 may not pass through the guide portion 880.

The first groove 884 and the second groove 886 may have different widthsin the Y-axis direction. The first groove 884 has a larger width thanthe supporting portion 832 and the second groove 886 has a larger widththan the contact portion 822. The second groove 886 has a wall surface887 on the side of the optical fiber tape 870. The wall surface 887 maybe a flat surface having the Y-axis direction as the normal direction.

The fixing member 840 includes a first fixing portion 843 and a secondfixing portion 845. The first fixing portion 843 fixes the ferrule 860to the housing 810 in the Z-axis direction perpendicular to the mountingsurface 813. The second fixing portion 845 fixes the ferrule 860 to thehousing 810 in the Y-axis direction.

The first fixing portion 843 includes a base 841, a first pressingportion 830, and the supporting portion 832. The base 841 includes twowall portions 842 and a bridge portion 844 which connects the two wallportions 842. The base 841 is a rigid member and gives rigidity to thefixing member 840. The two wall portions 842 are provided so as to beperpendicular to the mounting surface 813, to extend in parallel to theY-axis direction, and to face each other. The bridge portion 844 isparallel to the mounting surface 813, extends in a directionperpendicular to the Y-axis direction, and connects the two wallportions 842 at the upper end of the wall portion 842.

The first pressing portion 830 is provided in the base 841 and pressesthe ferrule 860 from the side opposite to the mounting surface 813. Thefirst pressing portion 830 may be two leaf springs. The leaf spring haselastic force for pressing the ferrule 860 to the mounting surface 813.One end of each leaf spring is fixed to the upper end of thecorresponding wall portion 842 of the base 841 and the leaf springextends to the base 841 opposite to thereto. The other end of the leafspring which is not fixed to the base 841 presses the ferrule 860 to themounting surface 813.

The base 841 includes the two bridge portions 844. The two leaf springsare provided between the two bridge portions 844 so as to face eachother. Before the fixing member 840 is fitted to the housing 810, theother end of the leaf spring which presses the ferrule 860 is locatedbelow the surface of the bridge portion 844 in the Z-axis direction. Aprotective structure 844 a with a plate shape which extends in thenegative Y-axis direction is provided in the bridge portion 844 close tothe contact portion 822.

The supporting portion 832 extends from the lower end of each wallportion 842 to the opposite wall portion 842. The distance between thelower end of the wall portion 842 and the surface of the supportingportion 832 which extends to the opposite wall portion 842 in the Z-axisdirection may be substantially equal to the thickness of the mountingportion 812 in the Z-axis direction. The supporting portion 832 mayinclude two lower L-shaped portions provided in the base 841. The lowerL-shaped portion has one end which is fixed to the lower end of the wallportion 842 of the base 841 opposite to the optical fiber tape 870 andthe other end which supports the rear surface of the mounting portion812. The two lower L-shaped portions extends from the lower end of thewall portion 842 in a direction in which it becomes further away fromthe wall portion 842 along the Z-axis direction and extends to theopposite wall portion 842. The two supporting portions 832 may beprovided so as to face each other. The two lower L-shaped portionsextend a distance of about 1 mm to 5 mm from the wall portion 842 in adirection close to the Y-axis.

The second fixing portion 845 includes a second pressing portion 820 andthe contact portion 822. The second pressing portion 820 is provided inthe base 841 and pressing the ferrule 860 to the light input/outputportion 814 in the Y-axis direction. The second pressing portion 820 hasa first state in which the second pressing portion 820 presses theferrule 860 to the light input/output portion 814 in the Y-axisdirection and a second state in which the second pressing portion 820does not press the ferrule 860 to the light input/output portion 814.The second pressing portion 820 may include two springs which areprovided in the corresponding base 841. Each spring may be formed ineach base 841 so as to be symmetric with respect to a middle linebetween the two bases 841.

The second pressing portion 820 extends from an end of each wall portion842 opposite to the contact portion 822 in the Y-axis direction, extendsto the opposite wall portion 842, and extends to the contact portion 822in the Y-axis direction. However, the second pressing portion 820 is notlimited to the above-mentioned shape. Each of the two springs has oneend which is fixed to the rear end of the wall portion 842 of the base841 and the other end which presses the ferrule 860 in the Y-axisdirection. The rear end of the wall portion 842 indicates a side end ofthe wall portion 842 close to the optical fiber tape 870.

When the second pressing portion 820 is in the first state, the contactportion 822 comes into contact with the housing 810 and fixes the secondfixing portion 845 to the housing 810. For example, when the secondpressing portion 820 is in the first state and presses the rear end ofthe ferrule 860 in a first direction facing the light input/outputportion 814, the contact portion 822 presses the housing 810 in adirection opposite to the first direction to fix the second fixingportion 845.

The contact portions 822 are formed so as to extend from the oppositesurfaces of the wall portions 842 to the opposite wall portions 842. Theopposite surfaces mean the surfaces of the wall portions 842 which faceeach other. The contact portion 822 is formed so as to extend from anend, which is close to the light input/output portion 814, of the endsof the wall portion 842 in the Y-axis direction. The distance betweenthe opposite surfaces of the two wall portions 842 is substantiallyequal to the distance between two end surfaces, in which the grooves areformed, in the two guide portions 880.

The contact portions 822 includes two lateral L-shaped portions whichare formed in the two bases 841 so as to be symmetric with respect to amiddle line between the two bases 841. Each lateral L-shaped portionextends from the end of the wall portion 842 in a direction in which itbecomes further away from the end of the wall portion 842 along theY-axis direction and extends to the opposite wall portion 842. Thelateral L-shaped portion extends a distance of about 1 mm to 5 mm fromthe wall portion 842 to the opposite wall portion 842.

The first fixing portion 843 and the second fixing portion 845 areformed in the common base 841. The second pressing portion 820 ischanged from the second state to the first state to move the base 841relative to the mounting portion 812 in the Y-axis direction. Forexample, when the second pressing portion 820 presses the rear end ofthe ferrule 860, the base 841 is moved in a direction opposite to thepressing direction by reaction force to the pressing force. The firstfixing portion 843 is moved from a second position to a first positionwith the movement of the base 841. For example, pressing working using adie may be performed for one metal plate to form the first fixingportion 843 and the second fixing portion 845.

As illustrated in FIGS. 55 and 56, the ferrule 860 is attached to thelight input/output portion 814 and is fixed to the housing 810 by thefixing member 840. In this state, the protective structure 844 a coversthe opening portion 814 a of the light input/output portion 814.Therefore, in the actual use, the optical element accommodated in thelight input/output portion 814 is protected from, for example, dust.

FIG. 57 is a diagram illustrating an optical module to which aprotective structure according to another embodiment is applied. FIG. 58is an exploded view illustrating the optical module illustrated in FIG.57. An optical module 800A illustrated in FIGS. 57 and 58 differs fromthe optical module 800 illustrated in FIGS. 55 and 56 in that a fixingmember 840A and a ferrule 860A replace the fixing member 840 and theferrule 860, respectively.

The fixing member 840A differs from the fixing member 840 in that abridge portion 844A without the protective structure 844 a replaces thebridge portion 844. In addition, the ferrule 860A differs from theferrule 860 in that it includes a plate-shape protective structure 868.In FIG. 58, for convenience of explanation, the protective structure 868is transparently illustrated.

As illustrated in FIGS. 57 and 58, the ferrule 860A is attached to thelight input/output portion 814 and is fixed to the housing 810 by thefixing member 840A. In this state, the protective structure 868 coversthe opening portion 814 a of the light input/output portion 814.Therefore, in the actual use, an optical element accommodated in thelight input/output portion 814 is protected from, for example, dust.

In the above-described embodiment, the housing of the optical module hasthe waveguide introduction opening. However, when a circuit substrate inwhich an optical waveguide does not protrude from the surface ismounted, a housing without the waveguide introduction opening may beused. That is, for example, the frame member may have a square shapewithout an opening. However, it is preferable that the frame member havea U-shape in order to increase the arrangement area of the LGA.

The optical waveguide provided on the circuit substrate is not limitedto the organic optical waveguide. Any optical waveguide may be providedon the circuit substrate as long as it protrudes from the surface of thesubstrate. For example, a ridge optical waveguide, such as a siliconwire waveguide, an optical fiber sheet, or a PLC chip may be used as theoptical waveguide.

A method for mounting the optical module on the circuit substrate is notlimited to the flip-chip bonding method. For example, the optical modulemay be mounted on the circuit substrate by reflow or solder studwelding. In addition, a communication system using the optical module orthe circuit substrate may be constructed.

As described above, the invention is mainly useful for opticalcommunication.

Although the invention has been described with respect to specificembodiments for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art that fairly fall within the basic teaching herein setforth.

What is claimed is:
 1. A method of protecting an optical module,comprising: preparing an optical module including a lens element; andattaching a protector to the optical module in a Manner that theprotector covers a surface of the lens element, wherein the opticalmodule includes a housing including an internal space that has anopening formed in a substrate mounting surface, and an element mountingsurface that forms a portion of an inner surface of the internal space,a waveguide introduction opening that is connected to the internalspace, an optical element that is mounted on the element mountingsurface, an electronic element that is mounted on the element mountingsurface and is connected to the optical element, the lens element thatis arranged so as to correspond to the optical element, and a holderthat holds the lens element at the arrangement position, and theprotector is inserted through the waveguide introduction opening.
 2. Themethod according to claim 1, wherein the optical module further includesan attachment structure to attach the protector, the attachmentstructure is a slit that is formed on the holder, the protector includesa plate-shaped portion, and in the attaching, a part of the plate-shapedportion is inserted into the slit.
 3. The method according to claim 2,wherein the waveguide introduction opening is formed in a side surfaceintersecting the substrate mounting surface, the protector includes theplate-shaped portion having one end which is to be inserted into theslit and a spring portion, having a U-shape when the spring portiontogether with the plate-shaped portion is viewed from a side surface ofthe protector, covers the waveguide introduction opening, and sandwichesthe optical module in a thickness direction of the optical module. 4.The method according to claim 1, further comprising: removing theprotector from the optical module.
 5. The method according to claim 1,further comprising: mounting, after the attaching of the protector, theoptical module, to which the protector is attached, on a circuitsubstrate.
 6. The method according to claim 1, farther comprising:mounting, after the attaching of the protector, the optical module, towhich the protector is attached, on a circuit substrate in a manner thatthe substrate mounting surface faces the circuit substrate, attaching aheight adjuster having a height adjustment portion to the optical modulein a manner that a height of a lower end of the height adjustmentportion at the waveguide introduction opening is substantially the sameas or less than a height of the substrate mounting surface, and fillinga gap between the circuit substrate and the optical module to which theheight adjuster is attached with an underfill material.
 7. A method ofprotecting an optical module, comprising: preparing an optical moduleincluding a lens element; and attaching a protector to the opticalmodule in a manner that the protector covers a surface of the lenselement, wherein the optical module includes a circuit substrate, ahousing that covers the circuit substrate, a light input/output portionformed on the circuit substrate, and the lens element accommodated inthe light input/output portion, the housing includes guide portionsformed at a leading end of the housing to guide an optical connector,which is to be connected to the light input/output portion, to the lightinput/output portion, and the protector includes a front protectiveportion having a plate shape, an upper protective portion, which is acover having a rectangular parallelepiped shape, extending from thefront protective portion in a direction perpendicular to a main surfaceof the front protective portion and having openings formed in a lowersurface and a surface opposite to the front protective portion, twofixing arms extending from the front protective portion along respectiveside surface of the upper protective portion, a lower protective surfaceextending from the front protective portion along the opening formed inthe lower surface of the upper protective portion, and a substratefitting portion extending from the lower protective portion and forminga step portion together with the lower protective portion.
 8. The methodaccording to claim 7, wherein the optical module includes guideportions, formed on the housing, as an attachment structure to attachthe protector, and in the attaching of the protector, the fixing armsare fitted to the guide portions.
 9. The method according to claim 7,further comprising: removing the protector from the optical module. 10.The method according to claim 7, further comprising: mounting, after theattaching of the protector, the optical module, to which the protectoris attached, on the circuit substrate.
 11. A method of protecting anoptical module, comprising: preparing an optical module including a lenselement; and attaching a protector to the optical module in a mannerthat the protector covers a surface of the lens element, wherein theoptical module includes a circuit substrate, a housing that covers thecircuit substrate, a light input/output portion formed on the circuitsubstrate, and the lens element accommodated in the light input/outputportion, the housing includes guide portions formed at a leading end ofthe housing, the guide portions guiding an optical connector, which isto be connected to the light input/output portion, to the lightinput/output portion, the optical module further includes a fixingmember that detachably fixes the optical connector to the housing, andthe protector is a protective structure provided on the fixing member.12. The method according to claim 11, further comprising: removing theprotector from the optical module.
 13. The method according to claim 11,further comprising: mounting, after the attaching of the protector, theoptical module, to which the protector is attached, on the circuitsubstrate.
 14. A method of protecting an optical module, comprising:preparing an optical module including a lens element; and attaching aprotector to the optical module in a manner that the protector covers asurface of the lens element, wherein the optical module includes acircuit substrate, a housing that covers the circuit substrate, a lightinput/output portion formed On the circuit substrate, and the lenselement accommodated in the light input/output portion, the housingincludes guide portions formed at a leading end of the housing, theguide portions guiding an optical connector, which is to be connected tothe light input/output portion, to the light input/output portion andthe protector is a protective structure provided on the opticalconnector.
 15. The method according to claim 14, further comprising:removing the protector from the optical module.
 16. The method accordingto claim 14, further comprising: mounting, after the attaching of theprotector, the optical module, to which the protector is attached, onthe circuit substrate.